An Environmental Streamflow Assessment for the Santiam River Basin, Oregon

By John C. Risley, J. Rose Wallick, Joseph F. Mangano, and Krista L. Jones

Prepared in cooperation with the U.S. Army Corps of Engineers

Open-File Report 2012–1133

U.S. Department of the Interior U.S. Geological Survey

Cover: North Santiam River downstream from Detroit Lake near Niagara at about river mile 57. (Photograph by Casey Lovato, U.S. Geological Survey, June 2011.)

Prepared in cooperation with the U.S. Army Corps of Engineers

An Environmental Streamflow Assessment for the Santiam River Basin, Oregon

By John C. Risley, J. Rose Wallick, Joseph F. Mangano, and Krista L. Jones

Open-File Report 2012–1133

U.S. Department of the Interior U.S. Geological Survey

U.S. Department of the Interior KEN SALAZAR, Secretary

U.S. Geological Survey Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation: Risley, J.C., Wallick, J.R., Mangano, J.F., and Jones, K.F, 2012, An environmental streamflow assessment for the Santiam River basin, Oregon: U.S. Geological Survey Open-File Report 2012-1133, 60 p. plus appendixes.

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Contents Abstract ...... 1 Introduction ...... 2 Scope of the Study ...... 2 Purpose of the Report ...... 2 Description of the Study Area ...... 4 Study Framework ...... 6 Streamflow Regulation ...... 8 Previous Santiam River basin Studies ...... 10 Environmental Regulatory Issues ...... 11 Methods ...... 12 Streamflow Data ...... 12 Measured and Estimated Streamflow ...... 12 Computed Unregulated Streamflow ...... 14 Computed Regulated Streamflow ...... 14 Bankfull Discharge Estimation Methods ...... 14 Indicators of Hydrologic Alteration ...... 16 Water-Use Compilation ...... 18 North Santiam River ...... 18 South Santiam River ...... 18 Main-Stem Santiam River...... 19 Pre- and Post-Dam Comparisons ...... 19 Streamflow Assessment ...... 20 North Santiam River ...... 21 South Santiam River ...... 32 Main-Stem Santiam River ...... 39 Geomorphic and Ecological Synopsis ...... 43 Geomorphic Characteristics of Study Reaches ...... 44 North Santiam River Channel Morphology ...... 44 South Santiam River Channel Morphology...... 47 Main-Stem Santiam River Channel Morphology ...... 49 Terrestrial and Aquatic Habitats and Key Species ...... 50 Potential Geomorphic and Ecological Response to Environmental Flow Releases ...... 51 Future Studies ...... 52 Streamflow Data and Analysis ...... 53 Bed-Material Transport Rates and Sediment Budget ...... 53 Detailed Channel and Flood-Plain Morphology Assessment ...... 54 Terrestrial and Aquatic Responses ...... 54 Summary ...... 55 Acknowledgements...... 57 References Cited ...... 57 Appendix A. Streamflow Data Time-Series Extension ...... 61 Appendix B. U.S. Army Corps of Engineers Computed Unregulated Streamflow Data Time Series ...... 61 Appendix C. Indicators of Hydrologic Alteration Results ...... 66 Appendix D. Description of Study Reaches ...... 66

iii

Figures Figure 1. Map showing major streams and dams in the Santiam River basin, Oregon...... 3 Figure 2. Diagram showing profile of the Santiam River basin, Oregon...... 4 Figure 3. Map showing geology of the Santiam River basin, Oregon ...... 5 Figure 4. Map showing location of study reaches, Santiam River, Oregon...... 7 Figure 5. Diagram showing dams and selected streamflow gaging stations in the Santiam River basin, Oregon...... 9 Figure 6. Graph showing daily mean streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water years 1922–2011...... 21 Figure 7. Graph showing mean daily streamflow in Reach 1 at North Santiam River at Niagara, Oregon (14181500), water years 1953–2009...... 22 Figure 8. Graph showing mean daily streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water years 1953–2009...... 22 Figure 9. Graph showing mean daily streamflow in Reach 3 at North Santiam River at Green’s Bridge near Jefferson, Oregon (14184100), water years 1953–2009...... 23 Figure 10. Graph showing daily mean streamflow in Reach 1 at North Santiam River at Niagara, Oregon (14181500), water year 1975...... 24 Figure 11. Graph showing daily mean streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water year 1975...... 24 Figure 12. Graph showing daily mean streamflow in Reach 3 at North Santiam River at Green’s Bridge near Jefferson, Oregon (14184100), water year 1975...... 25 Figure 13. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 1 at North Santiam River at Niagara, Oregon (14181500), water years 1953–2009...... 31 Figure 14. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water years 1953–2009...... 31 Figure 15. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 3 at North Santiam River at Green’s Bridge near Jefferson, Oregon (14184100), water years 1953–2009...... 32 Figure 16. Graph showing daily mean streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1924–2011...... 33 Figure 17. Graph showing mean daily streamflow in Reach 4 at Middle Santiam River at mouth near Foster, Oregon (14186500), water years 1967–2009...... 34 Figure 18. Graph showing mean daily streamflow in Reach 5 at South Santiam River at Foster, Oregon (14186700), water years 1967–2009...... 34 Figure 19. Graph showing mean daily streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1967–2009...... 35 Figure 20. Graph showing daily mean streamflow in Reach 4 at Middle Santiam River at mouth near Foster, Oregon (14186500), water year 1975...... 36 Figure 21. Graph showing daily mean streamflow in Reach 5 at South Santiam River at Foster, Oregon (14186700), water year 1975...... 36 Figure 22. Graph showing daily mean streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water year 1975...... 37 Figure 23. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 4 at Middle Santiam River at mouth near Foster, Oregon (14186500), water years 1967–2009...... 38

Figure 24. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 5 at South Santiam River at Foster, Oregon (14186700), water years 1967–2009...... 38 Figure 25. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1967–2009...... 39 Figure 26. Graph showing daily mean streamflow in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water years 1940–2011...... 40 Figure 27. Graph showing mean daily streamflow in Reach 7 at Santiam River at Jefferson , Oregon (14189000), water years 1953–2009...... 41 Figure 28. Graph showing daily mean streamflow in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water year 1975...... 42 Figure 29. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water years 1953–2009...... 43 Figure 30. Aerial photograph showing channel and flood-plain morphology in study Reach 1 of the Santiam River basin, Oregon, on the North Santiam River...... 44 Figure 31. Surficial geology and revetments for alluvial segments of the Santiam River, Oregon, study area...... 46 Figure 32. Aerial photograph showing channel and flood-plain morphology in study Reach 3 of the Santiam River basin, Oregon, on the North Santiam River...... 47 Figure 33. Aerial photograph showing channel and flood-plain morphology in study Reach 5 of the Santiam River basin, Oregon, on the South Santiam River...... 48 Figure 34. Aerial photograph showing channel and flood-plain morphology in study Reach 6 of the Santiam River basin, Oregon, on the South Santiam River...... 49 Figure 35. Aerial photograph showing channel and flood-plain morphology in study Reach 7 of the Santiam River basin, Oregon, Santiam River main stem...... 50 Tables Table 1. Study reach locations in the Santiam River basin, Oregon ...... 8 Table 2. Dams in the Santiam River Basin, Oregon ...... 10 Table 3. Minimum and maximum streamflow objectives below Big Cliff and Foster Dams ...... 11 Table 4. U.S. Geological Survey streamflow gaging stations in the Santiam River basin, Oregon ...... 13 Table 5. Study-reach streamflow gaging stations and bankfull discharge and flood estimates, Santiam River basin, Oregon...... 15 Table 6. Indicators of Hydrologic Alteration streamflow statistics at study reach streamflow gaging stations based on unregulated streamflow conditions in the Santiam River basin, Oregon, for water years 1953–2009...... 17 Table 7. Salem, Oregon, and Waterloo, Oregon, median monthly precipitation totals...... 20 Table 8. Pre- and post-dam flood statistics for selected Santiam River basin, Oregon, streamflow gaging stations, computed from annual peak streamflow data based on the Bulletin 17B Log Pearson III method...... 26 Table 9. One-day maximum annual streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon...... 27 Table 10. Seven-day minimum annual streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon...... 28 Table 11. Median monthly streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon ...... 29 Table 12. Streamflow exceedance statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon...... 30 v

Conversion Factors Inch/Pound to SI Multiply By To obtain Length inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km)

Area square yard (yd2) 0.08361 square meter (m2) square mile (mi2) 2.590 square kilometer (km2)

Volume cubic foot (ft3) 0.02832 cubic meter (m3) acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) cubic foot per second per square mile 0.01093 cubic meter per second per [(ft3/s)/mi2] square kilometer [(m3/s)/km2]

An Environmental Streamflow Assessment for the Santiam River Basin, Oregon

By John C. Risley, J. Rose Wallick, Joseph F. Mangano, and Krista L. Jones

Abstract and post-dam periods, which suggests that the construction and operation of the dams since the The Santiam River is a tributary of the 1950s and 1960s are a primary cause of altera- Willamette River in northwestern Oregon and tions to the Santiam River basin streamflow re- drains an area of 1,810 square miles. The U.S. gime. Army Corps of Engineers (USACE) operates four dams in the basin, which are used primarily for In addition to the streamflow analysis, this flood control, hydropower production, recreation, report provides a geomorphic characterization of and water-quality improvement. The Detroit and the Santiam River basin and the associated con- Big Cliff Dams were constructed in 1953 on the ceptual framework for assessing possible geo- North Santiam River. The Green Peter and Foster morphic and ecological changes in response to Dams were completed in 1967 on the South San- river-flow modifications. Suggestions for future tiam River. The impacts of the structures have biomonitoring and investigations are also provid- included a decrease in the frequency and magni- ed. This study was one in a series of similar tribu- tude of floods and an increase in low flows. For tary streamflow and geomorphic studies conduct- three North Santiam River reaches, the median of ed for the Willamette Sustainable Rivers Project. annual 1-day maximum streamflows decreased The Sustainable Rivers Project is a national effort 42–50 percent because of regulated streamflow by the USACE and The Nature Conservancy to conditions. Likewise, for three reaches in the develop environmental flow requirements in reg- South Santiam River basin, the median of annual ulated river systems. 1-day maximum streamflows decreased 39–52 percent because of regulation. In contrast to their effect on high flows, the dams increased low flows. The median of annual 7-day minimum flows in six of the seven study reaches increased under regulated streamflow conditions between 60 and 334 percent. On a seasonal basis, median monthly streamflows decreased from February to May and increased from September to January in all the reaches. However, the magnitude of these impacts usually decreased farther downstream from dams because of cumulative inflow from unregulated tributaries and groundwater entering the North, South, and main-stem Santiam Rivers below the dams. A Wilcox rank-sum test of monthly precipitation data from Salem, Oregon, and Waterloo, Oregon, found no significant difference between the pre-

Introduction Scope of the Study In 2002, The Nature Conservancy (The Na- As a continuation of the Willamette Sustain- ture Conservancy) and the U.S. Army Corps of able Rivers Project, the streamflow and geo- Engineers (USACE) formed the Sustainable Riv- morphic analyses from this study will assist the ers Project (The Nature Conservancy, 2009), a USACE and The Nature Conservancy in develop- partnership aimed at developing, implementing, ing an environmental flow framework for the and refining environmental flow requirements Santiam River basin. The framework will sup- downstream from dams. Environmental flows can plement a broader assemblage of ecological, hy- be defined as the streamflow needed to sustain drologic, and geomorphologic baseline data. The ecosystems while continuing to meet human analyses include an assessment of changes to the needs. Developing environmental flow require- ecosystem resulting from anthropogenic activi- ments typically involves a collective process of ties, such as dam operations and water withdraw- stakeholders to identify and prioritize streamflow als that have taken place in the basin. objectives. The process is a series of steps and The goals of this study are to analyze stream- feedback loops that include defining the streamflow trends in the main reaches of the Santiam flow requirements, implementing them into the River basin and describe geomorphic and biolog- dam operations, monitoring and modeling the ical conditions to facilitate the development of streamflow changes and their effect on the river environmental flow guidelines. Tasks to achieve ecosystem, and then adjusting and refining the these goals include: streamflow requirements if necessary. In addition to dams, other anthropogenic factors in a water- 1. Characterize streamflows in reaches under shed can contribute to freshwater ecosystem deg- regulated and unregulated conditions. radation, such as water diversions, channel re- 2. Qualitatively describe dominant geomorphic vetment, timber harvest, wetland draining, inva- and ecologic issues in reaches that could be sive species, gravel mining, and other factors, affected by environmental flow modifica- which also are commonly considered during the tions. development process (Tharme, 2003; Acreman 3. Communicate study results in a report and at and Dunbar, 2004; Richter and others, 2006; The future environmental flow workshops. Nature Conservancy, 2009). Purpose of the Report The Santiam River environmental flow study is a collaborative effort of the USACE, The Na- This report will provide Santiam River basin ture Conservancy, and the U.S. Geological Sur- stakeholders with a compilation of streamflow conditions under regulated and unregulated con- vey (USGS) to develop environmental flow requirements for the Santiam River, which is a trib- ditions in various reaches in the basin that are de- utary of the Willamette River in northwestern Or- fined by their geomorphic and ecological charac- egon (fig. 1). teristics. Using streamflow data and the results from the analysis of the data, it will be possible to identify the rate, frequency, duration, and timing of flow releases from Santiam River basin dams needed at downstream locations to achieve specific ecological and geomorphic objectives.

Figure 1. Map showing major streams and dams in the Santiam River basin, Oregon.

Description of the Study Area north of Albany. Elevations in the basin range from 162 ft at the Willamette confluence to The Santiam River basin is a subbasin of 10,497 ft at the summit of Mt. Jefferson. The riv- 1,810 mi2 within the Willamette River basin in er channel slope, within the study area down- northwestern Oregon (fig. 1). Major tributaries in stream from the dams, ranges from less than 0.1 the Santiam River basin include the North San- percent for the lower reach between the North tiam River, Little North Santiam River, Middle and South Santiam River confluences to almost 1 Santiam River, South Santiam River, Thomas percent for the North Santiam River below Big Creek, and Crabtree Creek. The North Santiam Cliff Dam (fig. 2). The basin has long, cool, wet River begins high in the Cascade Range near winters and warm, dry summers. Average daily Three Fingered Jack mountain and flows more maximum and minimum temperatures at Stayton than 100 mi before it joins the South Santiam from 1951 to 2011 were 63 and 42°F, respective- River about 2 mi upstream from Jefferson. The ly. Average annual precipitation at Stayton for South Santiam River begins at a lower elevation this period was 52.4 in. Because of greater pre- in the Western Cascades, west of the McKenzie cipitation at higher elevations, the mean annual River basin, and flows about 70 mi before joining precipitation for the entire Santiam River basin is the North Santiam River. From Jefferson, the 78.2 in. (1971–2000) (U.S. Geological Survey, main-stem Santiam River flows about 9 mi before 2012). it joins the Willamette River south of Salem and

Figure 2. Diagram showing profile of the Santiam River basin, Oregon.

Higher elevation areas are underlain by strained flood plain underlain by Quaternary al- young, relatively permeable material consisting luvium (fig. 3). The economy of the Santiam of High Cascade volcanic rocks and glacial de- River basin is supported by agriculture, timber posits. Middle and lower elevations of the basin harvesting, recreation, and manufacturing. Ap- contain the older, less permeable, weathered vol- proximately 70 percent of the basin is forested. canic material of the Western Cascades. The low- Timber is harvested on both private and Federal er reach of the river, near the Willamette River lands. Higher elevation areas in the basin are confluence, mainly comprises a wide, uncon- managed by the Willamette National Forest.

Figure 3. Map showing geology of the Santiam River basin, Oregon.

Study Framework from Foster Dam to RM 23.4 (upstream from USGS streamflow gaging station (hereinafter The Santiam River system in the study area “gage”) at Waterloo [14187500]) and from RM was divided into seven reaches, each having dis- 23.4 to the North Santiam River confluence, re- tinct streamflow, geomorphic, and ecological spectively. The final reach, Reach 7, extends conditions (fig. 4, table 1). The North Santiam from confluence of the North and South Santiam River portion of the study area was divided into Rivers through Jefferson to the Willamette River three reaches. Reach 1 extends from Detroit Dam confluence. For all reaches where the down- to the confluence of the Little North Santiam stream boundary is near a major stream conflu- River. Reach 2 continues downstream to river ence, the downstream boundary was set just up- mile (RM) 26 near Stayton. Reach 3 continues stream from the confluence. Streamflow from the downstream to the South Santiam River conflu- confluent stream is included in the streamflow of ence. The South Santiam River basin was also the next downstream reach. This was done to divided into three reaches. Reach 4 is along the minimize the difference in streamflow between Middle Santiam River, a tributary of the South both ends of the reach and to use a single repre- Santiam River, between Green Peter Dam and sentative reach discharge in the analyses. Foster Lake reservoir. Reaches 5 and 6 extend

Figure 4. Map showing location of study reaches, Santiam River basin, Oregon.

Table 1. Study reach locations in the Santiam River basin, Oregon.

Upstream Reach Reach end river length number River name Upstream end description mile Downstream end description (miles) Northern basin 1 North Santiam Detroit Dam 60.9 Little North Santiam River con- 21.7 fluence 2 North Santiam Little North Santiam River 39.2 Below Stayton, Oregon 13.2 confluence 3 North Santiam Below Stayton, Oregon 26.0 South Santiam confluence 14.2

Southern basin 4 Middle Santiam Green Peter Dam 5.5 Foster Dam 5.5 5 South Santiam Foster Dam 38.1 Above Waterloo, Oregon 14.7 6 South Santiam Above Waterloo, Oregon 23.4 N. Santiam River confluence 23.4

Lower basin 7 Lower Santiam North and South Santiam Riv- 11.8 Willamette confluence 11.8 er confluence

Streamflow Regulation Green Peter Dam, is used to produce hydropower and regulate power-generating water releases The USACE operates four dams in the San- from Green Peter Dam. The Green Peter and Fos- tiam River basin (fig. 5, table 2). The Detroit and ter Dams have generators capable of producing a the Big Cliff Dams, on the North Santiam River, combined total of 100 megawatts. Surface-water were completed in 1953. In addition to flood con- withdrawals for urban water supply and irrigation trol and recreation uses, the Detroit Dam also are made at locations downstream from the dams. produces up to 100 megawatts of power. The The city of Salem withdraws approximately 67 smaller Big Cliff Dam, 3 mi downstream from ft3/s from the North Santiam River at RM 31.0 on the Detroit Dam, is also used for hydropower Geren Island (Oregon Water Resources Depart- production and for regulating power-generating ment, 2012). On the South Santiam River, an av- water releases from Detroit Dam. The Green Pe- erage of 90 ft3/s of streamflow (water years ter and Foster Dams, in the South Santiam River 1993–2011) was diverted mostly for municipal basin, were completed in 1968. The two dams water supply to the Lebanon-Santiam Canal at work in conjunction to provide flood control, hy- RM 20.8 as measured at the USGS gage on the dropower production, irrigation supply, recrea- canal (14187600). tion, water-quality improvement, and aquatic habitat. Foster Dam, about 7 mi downstream from

Figure 5. Diagram showing dams and selected streamflow gaging stations in the Santiam River basin, Oregon.

Table 2. Dams in the Santiam River Basin, Oregon. [Data from the U.S. Army Corps of Engineers, http://www.nwd-wc.usace.army.mil/report/, accessed October 27, 2011.] Abbreviations: fad, feet above North American Vertical Datum of 1988; na, not applicable; mi2, square miles; KW, kilowatt; HP, hydropower; FC, flood control; N, navigation; I, irrigation; F, fisheries; WQ, water-quality; RR, Reregulation; R, recreation.] Lake pool elevation Upstream Reservoir Maximum drainage useable Reservoir power out- Year Min. Max. area River storage surface area put Dam name River completed (fad) (fad) (mi2) mile (acre-feet) (acres) Reservoir use (KW) Detroit North Santiam 1953 1,450 1,574 435 60.9 321,000 3,500 FC, HP, N, F, I, 100,000 WQ, R Big Cliff North Santiam 1953 1,180 1,210 449 58.1 na na RR, HP, R 18,000 Green Peter Middle Santiam 1968 922 1,015 276 5.5 312,500 3,720 FC, HP, N, I, F, 80,000 WQ, R Foster South Santiam 1968 613 641 492 38.1 28,300 1,220 RR, FC, HP, N, I, 20,000 F, WQ, R

The USGS conducted studies pertaining to the effect of res-

10 Previous Santiam River basin Studies ervoir operations in the Santiam River basin on water tempera- Speers and Versteeg (1982) presented procedures for long- tures in and downstream from reservoirs. Laenen and Hanson term forecasts of spring-season water supply for Detroit reser- (1985) and Hanson and Crumrine (1991) simulated water tem- voir operations. Laenen and Risley (1997) and Lee and Risley peratures downstream from reservoirs on the North and South (2002) created a set of precipitation-runoff watershed models for Santiam Rivers using a daily mean, one-dimensional Lagrangian the entire Willamette River basin for water-quality and ground- computer model. More recent studies by Sullivan and Rounds water analyses, respectively. In these studies, the Santiam River (2004), Sullivan and others (2007), and Buccola and Rounds basin was divided into 22 subbasins, from which 22 watershed (2011) also simulated water temperatures on the North Santiam models were created. Thayer (1936a, 1936b) presented early re- River in and downstream from reservoirs using temporally and search on geology in the Santiam River basin. Helm and Leon- spatially detailed two-dimensional models. In addition to water ard (1977) described groundwater resources in the lower basin. temperatures, heavy flooding and landslides in the late 1990s Conlon and others (2005) described groundwater hydrologic resulted in a major water-quality concern over suspended sedi- conditions in the entire Willamette River basin, including the ment in North Santiam River. Uhrich and Bragg (2003) present- Santiam River basin. Fletcher and Davidson (1988) analyzed the ed a method for estimating suspended-sediment loads and yields geomorphic response to regulation and bank protection in the using turbidity data. Bragg and Uhrich (2010) presented a sus- lower section of the South Santiam River. Hill and Priest (1992) pended-sediment budget for the entire North Santiam River ba- described the geologic setting of the Santiam Pass area. Sherrod sin. Suspended sediment and turbidity in the basin are also de- and others (1996) presented an overview of geology, hydrology, scribed in Bragg and others (2007), Piatt and others (2011), and and geothermal resources in the North Santiam River basin. Sobieszcyk and others (2007).

Environmental Regulatory Issues In July 2008, NMFS released their decision on the Biological Assessment plans through a In early 1999, the National Marine Fisheries Willamette Project Biological Opinion (National Service (NMFS) listed Upper Willamette River Marine Fisheries Service, 2008a; 2008b). The Chinook salmon (Oncorhynchus tshawytscha) USFWS also released a Biological Opinion for and the Upper Willamette River steelhead (On- the Willamette River basin because they have ju- corhynchus mykiss) in the Santiam River basin risdiction over the Oregon chub (U.S. Fish and and other upper Willamette River basins as Wildlife Service, 2008). NMFS and the USFWS threatened under the Federal Endangered Species decided that the USACE Biological Assessment Act (ESA). In 1993, the U.S. Fish and Wildlife plans were insufficient for mitigating the effect of Service (USFWS) listed the Oregon chub (Ore- the water projects on critical habitat. The Biolog- gonichthys crameri) as endangered in Marion and ical Opinion ordered additional measures, which Linn Counties, which includes the Santiam River included improved fish passage, temperature con- basin. In 2010, the Oregon chub was reclassified trol, and changes in downstream streamflows. from endangered to threatened. As a result of the- The Biological Opinion includes flow-release se listings, the USACE submitted its first Biolog- targets for Big Cliff and Foster Dams for differ- ical Assessment in 2000 and a supplemental Bio- ent seasonal life histories for the ESA-listed fish logical Assessment in 2007 for the Willamette (table 3). The Biological Opinion also includes a River basin that included specific recovery plans measure for implementing environmental flow for the Santiam River basin (U.S. Army Corps of releases from the dams. Engineers, 2000, 2007).

Table 3. Minimum and maximum streamflow objectives below Big Cliff and Foster Dams. [Source: National Marine Fisheries Service, 2008]

Minimum Maximum Period Primary Use flow (ft3/s) flow (ft3/s) Big Cliff Dam September 1–October 15 Chinook spawning 1,500 3,000 October 16–January 31 Chinook incubation 1,200 February 1–March 15 Chinook rearing/adult migration 1,000 March 16–May 31 steelhead spawning 1,500 3,000 June 1–July 15 steelhead incubation 1,200 July 16–August 31 steelhead rearing 1,000

Foster Dam September 1–October 15 Chinook spawning 1,500 3,000 October 16–January 31 Chinook incubation 1,100 February 1–March 15 Chinook rearing 800 March 16–May 15 steelhead spawning 1,500 3,000 May 16–June 30 steelhead incubation 1,100 July 1–August 31 steelhead rearing 800

The Oregon Department of Environmental (14187500: 1923–2011). From 2005 to 2010, the Quality (ODEQ), as required under the Federal USGS also operated eight temporary streamflow Clean Water Act, released a stream-temperature measurement sites (14183430, 14183450, Total Maximum Daily Load (TMDL) plan in 14183500, 14183550, 14183570, 14183580, 2006 for the Willamette River basin (Oregon De- 14183585, and 14183590) in the vicinity of Ger- partment of Environmental Quality, 2006). en Island on the North Santiam River. (Map at Stream reaches in the North and South Santiam http://or.water.usgs.gov/northsantiam/sites/). River basins found to be thermally impaired and Streamflow and stage were measured intermit- not meeting state temperature standards for salm- tently at these sites during six summers to create onid rearing, spawning, and cold-water refuges, rating curves. One station was upstream from as a result of reservoir releases, channel geomor- Geren Island, five stations were in the north and phology alterations, streamflow diversions, and south channels around the island, and two sta- limited riparian shade, were placed on the Federal tions were in side diversion cannels. The purpose Clean Water Act section 303(d) list as having ex- of the data monitoring was to gain a better under- ceeded their temperature TMDL. standing of the spatial and temporal distribution of surface waters during low-flow conditions up- Methods stream and downstream from the island, in the alcoves and secondary channels, and near the Sa- For this study, various methods were em- lem municipal water-supply intakes. ployed to assess the effects of dams and withdrawals on streamflows. These included a compi- Seven of the gages from table 4 were repre- lation of measured and estimated daily mean gage sentative of flow conditions in the seven defined statistics under regulated and unregulated condi- study reaches and could be used in the statistical tions, bankfull streamflow estimation, pre- and analyses (table 5). Streamflow data for Reaches post-dam peak-flow analysis, and a pre- and post- 1, 2, 6, and 7 represented unregulated and regu- dam period climate comparison. lated flow conditions because they extended from the 1920s and 1930s to water year 2011. Howev- Streamflow Data er, for the other three reaches (Reaches 3, 4, and 5), it was necessary to augment the measured Measured and Estimated Streamflow streamflow period with computed regulated and The USGS began continuous streamflow computed unregulated daily mean streamflow monitoring within the Santiam River basin (table time series provided by the USACE. Microsoft® 4) in the 1920s. Eighteen of these stations were Excel® files containing measured and estimated active during water year 2011. The stations with daily mean streamflows for the seven reaches can the longest streamflow time series are the North be downloaded from the link in Appendix A. Santiam River at Mehama (14183000: 1921– 2011) and the South Santiam River at Waterloo

Table 4. U.S. Geological Survey streamflow gaging stations in the Santiam River basin, Oregon.—continued [A water year is from October 1 of the previous year to September 30. Abbreviations: mi2, square miles; *, stage or elevation data only; na, not applicable.] Drainage Station area Period of record number Streamflow station name (mi2) (water years) 14178000 North Santiam River below Boulder Creek near Detroit, Oregon 216 1928–2011 14178700 East Humbug Creek near Detroit, Oregon 7.32 1978–1994 14179000 Breitenbush River above French Creek near Detroit, Oregon 108 1932–1987; 1998–2011 14179100 French Creek near Detroit, Oregon 9.9 2002–2005 14180300 Blowout Creek near Detroit, Oregon 26.0 1998–2011 14180500 Detroit Lake near Detroit, Oregon 437 1953–2004* 14181500 North Santiam River at Niagara, Oregon 453 1938–2011 14181750 Rock Creek near Mill City, Oregon 14.8 2005–2008 14182400 Little North Santiam River below Canyon Creek near Mehama, Oregon 93.0 2007–2008 14182500 Little North Santiam River near Mehama, Oregon 112 1931–2011 14183000 North Santiam River at Mehama, Oregon 654 1921–2011 14184100 North Santiam River at Greens Bridge near Jefferson, Oregon 736 1964–1967; 2011 14185000 South Santiam River below Cascadia, Oregon 174 1935–2011 14185700 Middle Santiam River near Upper Soda, Oregon 74.6 1981–1994 14185800 Middle Santiam River near Cascadia, Oregon 104 1964–1981; 1988 14185880 Packers Gulch near Cascadia, Oregon 7.45 1983–1986 14185900 Quartzville Creek near Cascadia, Oregon 99.2 1963–2011 14186000 Middle Santiam River near Foster, Oregon 271 1931–1947 14186100 Green Peter Lake near Foster, Oregon 273 1974–2003* 14186200 Middle Santiam River below Green Peter Lake near Foster, Oregon 273 2010–2011* 14186500 Middle Santiam River at mouth near Foster, Oregon 287 1950–1966 14186600 Foster Lake at Foster, Oregon 492 1974–2003* 14186700 South Santiam River at Foster, Oregon 493 1966–1973 14187000 Wiley Creek near Foster, Oregon 51.8 1947–1973; 1988–2011 14187100 Wiley Creek at Foster, Oregon 62.3 1973–1988 14187200 South Santiam River near Foster, Oregon 557 1973–2011 14187500 South Santiam River at Waterloo, Oregon 640 1923–2011

Computed Unregulated Streamflow lated time series were computed are provided in Appendix B. The USACE compiled and computed unregulated daily mean streamflow time series for wa- For Reaches 1, 3, and 4, it was necessary to ter years 1936–2009 at North Santiam River at adjust the USACE unregulated daily mean Detroit Dam (upstream from 14181500), North streamflows using a drainage-area ratio to create Santiam River at Mehama (14183000), Middle unregulated streamflow conditions at the USGS Santiam River at Green Peter Dam (upstream gages in those reaches. Details of the adjustments from 14186500), South Santiam River at Foster are included in the Excel files for each reach Dam (14186700), South Santiam River at Water- (Appendix A). loo (14187500), and Santiam River at Jefferson (14189000) (Alan Donner, U.S. Army Corps of Computed Regulated Streamflow Engineers, written commun., 2011). These time USACE also provided this study with com- series are an estimate of streamflow (1936–2009) puted regulated daily mean streamflow time se- at these locations if the four USACE dams had ries for Big Cliff Dam (1960–2011), Green Peter not been constructed. For this study, these time Dam (1967–2011), and Foster Dam (1968–2011). series were used to evaluate the hydrologic effect The time series for Green Peter and Foster Dams of the dams by comparing pre- and post-dam were used to create the Reach 4 and 5 regulated streamflow conditions. streamflow time series, respectively, because The daily mean streamflow time series for measured USGS streamflow data were unavaila- the North Santiam River at Detroit Dam and the ble at these locations for these time periods. Middle Santiam River at Green Peter Dam were Bankfull Discharge Estimation Methods computed using USACE reservoir models. How- ever, the time series for the other locations were In geomorphology, bankfull discharge is computed by adding these simulated time series generally assumed to represent the geomorphical- with estimated downstream local inflows. The ly significant flow that fills the banks without inflow time series were computed using correla- spilling onto the flood plain. It is commonly used tions with nearby unregulated USGS streamflow as a streamflow metric in environmental flow records in the region. Details on how the unregu studies when creating flow prescriptions that will

meet the habitat needs of an aquatic or terrestrial species at vari- (table 5). Estimates based on the latter method are not included ous life stages. The estimation of bankfull discharge has substan- in the table because of insufficient channel detail in the data or tial uncertainty because it has to be estimated at a specific loca- because flow events had insufficient magnitude. tion and is not necessarily representative of a reach. Wolman and Bankfull flood stage and discharge estimates for gages in Miller (1960) defined bankfull discharge as having a recurrence Reaches 2, 6, and 7 were previously determined by the USACE interval of 1.5 years in a variety of rivers. However, that ap- using field-site-level surveys, aerial photography, and flood proach could not be used consistently in all seven study reaches, analyses (Keith Duffy, U.S. Army Corps of Engineers, written because not all the reaches have an adequate number of years of commun., 2011). The corresponding gages, which include North pre-dam peak-flow data to complete a flood-frequency analysis. Santiam River at Mehama, Oregon (14183000) (Reach 2), South For this study, several methods of estimating bankfull dis- Santiam River at Waterloo, Oregon (14187500) (Reach 6), and charge were compared and evaluated. These included bankfull- Santiam River at Jefferson, Oregon (14189000) (Reach 7), have discharge estimates provided by the USACE, unit-discharge es- the longest streamflow records in the Santiam River basin and timates based on USACE estimates, field observations at gages, also are used as flood-forecast sites by the U.S. National Weath- calculation of the 1.5-year peak-flow frequency, and channel er Service River Forecasting Center. cross-section plots derived from high-flow measurement data Table 5. Study-reach streamflow gaging stations and bankfull discharge and flood estimates, Santiam River basin, Oregon. 15 2 3

[Abbreviation: USACE, U.S. Army Corps of Engineers; LPIII, Bulletin 17B Log Pearson III flood frequency analysis; mi , square mile; ft /s, cubic feet per second; na, not available. River mile is distance from the nearest downstream confluence.] Bank full discharge estimates Unit LPIII flood frequency USACE Drainage discharge USGS field 1.5-year flood Reach Station area River USACE estimate estimate Pre-dam period of peak estimate number number Streamflow gaging-station name (mi2) mile (ft3/s) (ft3/s) (ft3/s) record (ft3/s) (ft3/s) 1 14181500 North Santiam River at Niagara, Oregon 453 57.3 na 11,100 3,000 1909–52 16,700 na

2 14183000 North Santiam River at Mehama, Oregon 654 38.7 17,000 na na 1906–52 28,500 30,500 3 14184100 North Santiam River at Greens Bridge 732 14.6 na 18,000 na na na na near Jefferson, Oregon 4 14186500 Middle Santiam River at mouth near Fos- 287 1.0 na 7,050 na 1950–66 23,100 na ter, Oregon 5 14186700 South Santiam River at Foster, Oregon 493 38.0 na 12,100 5,550 na na na

6 14187500 South Santiam River at Waterloo, Oregon 640 23.3 18,000 na na 1906–52 31,500 25,700

7 14189000 Santiam River at Jefferson, Oregon 1,790 9.6 35,000 na na 1908–52 62,400 55,900

For gages in the other study reaches, Reach 1 Waterloo (14187500), or Reach 7, Santiam River (14181500), Reach 3 (14184100), Reach 4 at Jefferson (14189000) because the USACE had (14186500), and Reach 5 (14186700), bankfull previously estimated bankfull discharge at those discharge was estimated using an average of the sites. unit discharges of the three USACE estimates for Using measured pre-dam annual peak-flow Reaches 2, 6, and 7. The unit discharges were data, the 1.5-year flood frequency, based on the computed by dividing the USACE estimates by Bulletin 17B Log Pearson III method (Interagen- the upstream drainage areas of the gages. The av- cy Committee on Water Data, 1982), was com- erage of the three unit discharges was 24.6 3 2 puted for the gages in Reaches 1, 2, 6, and 7. It (ft /s)/mi . This value was multiplied by the up- was not possible to compute a flood frequency stream drainage areas of the Reach 1, Reach 3, for the Reach 3 and Reach 5 gages, 14184100 Reach 4, and Reach 5 gages to get bankfull dis- and 14186700, respectively, because their records charge estimates for those reaches. did not contain peak-flow data during the pre- Field estimates of bankfull stage were made dam period. As shown in table 5, the 1.5-year by the USGS for this study in January 2011 at the flood frequencies were higher than the other gages for Reach 1, North Santiam River at Niaga- USACE bankfull discharge estimates for the ra, Oregon (14181500), and for Reach 5, South Reach 2 (14183000), Reach 6 (14187500), and Santiam River at Foster, Oregon (14186700). Reach 7 (14189000) gages. Stage height was estimated using a hand-held To estimate bankfull discharge from channel leveler because time and funding restrictions pre- cross-section plots, it is sometimes possible to cluded measuring stage heights using a transit create the plots using stage and discharge data and rod. At both gages, readings from outside from USGS discharge measurement notes from staff gages were taken while standing just below gages. With a detailed channel cross section dur- flood-plain level. The height of the observer was ing a measured high-flow event, bank and flood- then subtracted from the staff reading. With a plain features can sometimes be defined to esti- bankfull stage estimate, the bankfull discharge mate the bankfull stage. With a bankfull stage could be determined using the rating curve. In estimate, the bankfull discharge can be deter- comparison to the other two methods of bankfull mined from the rating curve. The bankfull stage discharge estimation, these field observation es- estimate could not be estimated at the Reach 1 timates were considerably smaller. gage on the North Santiam River at Niagara A major limitation with bankfull discharge (14181500) and the Reach 4 gage at the Middle estimates made from field observation is that Santiam River at the mouth near Foster their representation of the reach is limited to (1418650) because the channel cross-section proximity of the gage. It was not possible to plots from these high-flow events contained in- make a bankfull discharge field estimate at the sufficient detail to delineate the streambank and Reach 3 gage, South Santiam River at Green’s flood-plain features. Bankfull stage estimates for Bridge near Jefferson (14184100), because of Reach 3 gage on the North Santiam River at visual obstructions in the line of sight. It was also Green’s Bridge near Jefferson (14184200) and not possible to make a bankfull discharge field the Reach 5 gage on the South Santiam River at estimate at the Reach 4 gage, Middle Santiam Foster (14186700) were not made because the River at mouth near Foster (14186500) because it magnitude of high-flow measurements was insuf- was active only during the pre-dam period (1950– ficient. 66) and is now submerged beneath Foster Reser- voir. Field estimates were not made at gages for Indicators of Hydrologic Alteration Reach 2, North Santiam River at Mehama Developed by The Nature Conservancy for (14183000), Reach 6, South Santiam River at the Sustainable Rivers Project, the Indicators of

Hydrologic Alteration (IHA) software program magnitudes for the 2- and 10-year recurrence in- allows users to compute streamflow statistics that tervals using a Weibull distribution. can be used to quantify hydrologic changes re- Streamflow statistics in table 6 were comput- sulting from the construction of dams and diver- ed using data provided by the USACE represent- sion canals in a river basin (The Nature Conserv- ing unregulated streamflow conditions for each ancy, 2007). For a given daily mean streamflow reach. A common period (water years 1953– record, the program computes an extreme low- 2009) was used for all seven reaches. Like bank- flow threshold, high-flow threshold, small floods full flow estimates, estimates of low flows, pulse (2-year events), and large floods (10-year events) flows, small floods, and large floods are used in (table 6). The high-flow threshold, which is also environmental flow studies to define flow pre- the 25 percent streamflow exceedance, is analo- scriptions that will meet the habitat needs of an gous to a high-flow pulse. The extreme low-flow aquatic or terrestrial species at various life stages. category includes the lowest 10 percent of daily Output from the IHA program can be download- mean streamflows that are less than the high-flow ed at the link in Appendix C. threshold. The IHA program estimates flood

Table 6. Indicators of Hydrologic Alteration streamflow statistics at study reach streamflow gaging stations based on unregulated streamflow conditions in the Santiam River basin, Oregon, for water years 1953–2009. [Abbreviation: ft3/s, cubic feet per second.]

Extreme low-flow High-flow Reach Station threshold threshold 2-year flood 10-year flood number number Streamflow gaging station name (ft3/s) (ft3/s) (ft3/s) (ft3/s) 1 14181500 North Santiam River at Niagara, Oregon 635 2,810 21,300 32,200 2 14183000 North Santiam River at Mehama, Oregon 685 4,270 35,400 53,900 3 14184100 North Santiam River at Greens Bridge near Jefferson, 767 4,780 39,600 60,400 Oregon 4 14186500 Middle Santiam River at mouth near Foster, Oregon 130 2,190 20,700 33,200 5 14186700 South Santiam River at Foster, Oregon 210 3,420 32,600 49,900 6 14187500 South Santiam River at Waterloo, Oregon 223 3,980 35,800 59,100 7 14189000 Santiam River at Jefferson, Oregon 551 10,100 85,000 144,000

Water-Use Compilation ured (14184100) streamflow time series. Next, all major surface-water withdrawals between the two Major surface-water withdrawals along the gages (14183000 and 14184100) were subtracted lower reaches of the North Santiam, South San- from the estimated 14184100 streamflow time tiam, and Santiam Rivers were compiled in order series. Monthly surface-water withdrawals to quantify natural streamflow conditions. Much (2001–2011) for Salem, Stayton Water Control of the water-use data and information was from District, NORPAC Foods, and Sidney Irrigation the Oregon Water Resources Department website Cooperative were compiled and summed. This (http://www.wrd.state.or.us) and Sullivan and amount was offset by effluent from Stayton (3.33 Rounds (2004). ft3/s on a mean annual basis) at RM 27.5. Month- ly net water withdrawals were converted to daily North Santiam River values and then smoothed using a 30-day running For Reach 1, from Detroit Dam to the Little average. Estimated mean annual net water with- drawal between the two gages (14183000 and North Santiam River confluence, direct surface- 3 water withdrawals are minimal. The towns of 14184100) was 335 ft /s (water years 2001– Gates (RM 51.2) and Mill City (RM 47.5) with- 2010). draw 0.13 and 0.35 ft3/s on a mean annual basis, Prior to its subtraction from the estimated respectively, for municipal water supply. Howev- streamflow time series for Green’s Bridge near er, downstream from the Little North Santiam Jefferson (14184100), Salem municipal-use with- River confluence to RM 26 (Reach 2), surface- drawals and Stayton effluent return flows were water withdrawals are more significant. The city adjusted for population growth between 1950 and of Salem withdraws approximately 67 ft3/s on a 2011. Using Marion County population for 1950, mean annual basis from intakes near Geren Island 1960, 1970, 1980, 1990, 2000, and 2010 from the at RM 31. The city of Stayton and the Santiam U.S. Census, a regression was created to estimate Water Control District withdraw approximately the county population for each year from 1950 260 ft3/s on a mean annual basis at RM 29.5. At and 2011. Monthly-mean Salem municipal-use RM 27.0, NORPAC Foods withdraws 0.40 ft3/s withdrawals and Stayton effluent return flows for from June to October. In Reach 3, from RM 26 to the 2001 to 2010 were adjusted to 1950 using a the South Santiam River confluence, approxi- ratio of the population in the earlier year to the mately 40 ft3/s is withdrawn from May to Sep- population in 2010. However, estimated with- tember by the Sidney Irrigation Cooperative at drawals for irrigation use were not adjusted for RM 19.6. population growth on the assumption that irriga- Water-use data for the North Santiam River tion use has not increased as rapidly as municipal was used for extending the measured daily mean use has from 1951 to 2011. streamflow time series for the Reach 3 gage, North Santiam River at Green’s Bridge near Jef- South Santiam River ferson (14184100). The period of operation for For Reach 4, from Green Peter Dam to Fos- this station was from water years 1964 to 1967 ter Dam, withdrawals from the Middle Santiam and 2006 to 2011. To create a longer time series River (which flows into the South Santiam River) (water years 1951–2011) for this site, daily mean are minimal or nearly nonexistent. However, in streamflow data from the upstream gage, North Reach 5, downstream from Foster Dam to RM Santiam River at Mehama (14183000), were pro- 23.4, above the Waterloo gage (14187500), mean portionally adjusted to the increased drainage ar- annual water use reported by the City of Sweet ea of the Reach 3 Green’s Bridge near Jefferson Home was 1.76 ft3/s for water years 2001–2010. gage (14184100). These adjusted streamflows In Reach 6, which extends from the Waterloo were used to fill in missing periods in the meas- gage (14187500) to the North Santiam River con-

fluence, water is diverted from the South Santiam Pre- and Post-Dam Comparisons River through the Lebanon-Santiam Canal at RM Statistical and graphical comparisons were 20.9, upstream of Lebanon. For water years used to assess the effects of dams on streamflows. 1992–2011, mean annual streamflow was 89 ft3/s These included comparisons of annual peak and as measured at the USGS gage (14187600) on the daily mean streamflow data measured before and canal and near the canal diversion point on the after the dams were constructed. Comparisons river. Since 2007, withdrawals from the river to were also made of post-dam period measured dai- the canal have been as high as 200 ft3/s during the ly mean streamflows with the post-dam period summer. The canal water is used for irrigation, computed unregulated daily mean streamflows small project hydropower generation, and munic- provided by the USACE. ipal water supply for Lebanon and Albany. Leba- non withdrew 3.01 ft3/s (average for water years Comparisons of pre- and post-dam period 2001–2010) from the canal (Oregon Water Re- measured streamflow data were possible in four sources Department, 2012). Previously, the canal of the reaches, which had lengthy continuous diverted water from the South Santiam River at a streamflow records that began in the 1920s or location slightly downstream from Lebanon at 1930s. These included North Santiam River at RM 17.0 and was known as the “Albany-Santiam Niagara (14181500), North Santiam River at Me- Canal.” Mean annual streamflow in the canal dur- hama (14183000), South Santiam River at Water- ing this earlier period was 209 ft3/s (water years loo (14187500), and Santiam River at Jefferson 1926–1957) as measured at the inactive USGS (14189000). In using this method of comparison, gage (14188000) on the canal. it was necessary to determine whether climate was a contributing factor to changes in stream- In addition to the Sweet Home municipal flow by evaluating monthly precipitation data at water supply and the Lebanon-Santiam Canal, Salem and Waterloo from the pre- and post-dam other substantial diversions in the South Santiam periods. On the basis of a Wilcox rank-sum test, River are for irrigation. From RM 21.1 to the there was no significant difference in monthly North Santiam River confluence, mean direct sur- precipitation between the two periods. The p- face-water withdrawals for irrigation are 16.9 values for all the months, with the exception of ft3/s annually, on the basis of Oregon Water Re- February in Salem, were greater than 0.5 sources Department water-availability data (table 7). (Cooper, 2002; Oregon Water Resources De- partment, 2012).

Main-Stem Santiam River Surface-water withdrawals in Reach 7, from the confluence of the North and South Santiam Rivers to the Willamette River confluence, include the Jefferson municipal water supply and irrigation for agricultural. Mean annual water use reported by the City of Jefferson was 0.51 ft3/s for water years 2001–2010. Surface-water withdrawals for irrigation from the Santiam River in Reach 7 are 5.02 ft3/s on a mean annual basis based on Oregon Water Resources Department water-availability data (Cooper, 2002).

Table 7. Salem, Oregon, and Waterloo, Oregon, median monthly precipitation totals. [Source: Western Regional Climate Center (2012). Abbreviation: WY, water year. p-values less than 0.05 resulting from a Wilcox rank-sum test indicate there is a significant difference in the monthly precipitation totals between the pre-dam and post-dam periods. Salem and Waterloo precipitation data from stations 357500 and 359083, respectively.]

Salem, Oregon (North Santiam River basin) Waterloo, Oregon (South Santiam River basin)

Pre-dam Post-dam Pre-dam Post-dam 1935–1952 1953–2010 1935–1966 1967–2010 (inches) (inches) p-value (inches) (inches) p-value

WY total 41.1 39.6 0.56 41.6 45.0 0.34

January 5.34 6.43 0.51 5.29 6.98 0.58

February 5.57 4.28 0.03 4.74 4.41 0.47

March 4.02 3.82 0.92 4.80 4.55 0.78

April 1.88 2.44 0.12 2.62 3.25 0.08

May 1.60 1.90 0.68 1.86 2.20 0.47

June 0.98 1.17 0.47 1.11 1.57 0.06

July 0.36 0.23 0.30 0.03 0.26 0.14

August 0.35 0.38 0.66 0.20 0.57 0.28

September 1.38 1.20 0.83 1.26 1.37 0.19

October 2.87 2.89 0.65 3.30 3.18 0.79

November 5.36 6.05 0.72 6.63 6.47 0.78

December 6.25 6.95 1.00 5.59 7.13 0.59 Statistical metrics representing different en- the magnitude of floods, comparisons of meas- vironmental flow components, such as low flows ured daily mean streamflows and USACE com (7-day annual minimum, 95-percent exceedance), puted unregulated daily streamflows for a single high flows (1-day maximum annual, 5-percent water year (1975) also were included. Water year exceedence), floods (annual peak), and median 1975 data were used in the daily mean stream- monthly flows, were computed to compare pre- flow comparison plots because it approximates an and post-dam conditions. average year in the historic streamflow record Graphical comparisons of pre- and post- (water years 1939–2011) for the Santiam River at streamflow regulation include mean daily stream- Jefferson (14189000). flow plots. Mean daily streamflow for any one day, October 10, for example, is the arithmetic Streamflow Assessment mean of the discharge on all October 10s of the record, or a specified period of a record. This is Results from an assessment of the effects of different from daily mean streamflow, which is dams and surface-water withdrawals on the full defined as the mean streamflow for that one day. streamflow regime for the seven study reaches in Because a mean daily streamflow plot dampens the Santiam River basin are described below.

North Santiam River flood threshold was exceeded in the post-dam period were December 22, 1964, at 36,200 ft3/s The hydrologic effect of the Detroit and Big and February 7, 1996, at 46,700 ft3/s, respective- Cliff Dams, completed in 1953, is evident in the ly. The USACE estimated that these two events streamflow record at the USGS gage on the North would have been 91,600 and 96,400 ft3/s, respec- Santiam River at Mehama (14183000) (fig. 6). tively, had the dams not been constructed (fig. 6) Prior to dam regulation, daily mean streamflow (Alan Donner, U.S. Army Corps of Engineers, exceeded the USACE defined bankfull (17,000 written commun., 2011). ft3/s) and flood (30,500 ft3/s) threshold discharges on average 3.39 and 0.68 times per year, respectively, from 1922 to 1952. However, from 1953 to 2011, bankfull and flood threshold discharges were exceeded on average only 0.97 and 0.03 times per year, respectively. The two times the

Figure 6. Graph showing daily mean streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water years 1922–2011. A comparison of measured and computed (figs. 7–9), respectively. These streamflow altera- unregulated mean daily streamflows (water years tions are typical of locations downstream from 1953–2009) at North Santiam River gages in reservoirs used for hydropower production and Reaches 1–3 at Niagara (14181500), Mehama flood control. Flows are decreased in the spring (14183000), and Green’s Bridge (14184100) when the reservoirs are filling up. The increased showed that February–April streamflows de- fall flows are the result of reservoir drawdown creased and August–November streamflows in- each year prior to the annual flood season. creased under regulated streamflow conditions

Figure 7. Graph showing mean daily streamflow in Reach 1 at North Santiam River at Niagara, Oregon (14181500), water years 1953–2009.

Figure 8. Graph showing mean daily streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water years 1953–2009.

Figure 9. Graph showing mean daily streamflow in Reach 3 at North Santiam River at Green’s Bridge near Jefferson, Oregon (14184100), water years 1953–2009. Changes in seasonal streamflow patterns Using annual peak-flow data, flood frequen- caused by the dams is also evident in a compari- cies based on the Bulletin 17B Log Pearson III son of measured regulated and computed unregu- method were computed for the pre-dam and post- lated daily mean streamflows at these three gages dam periods for Niagara (14181500) and Me- during a single average hydrologic year (1975). hama (14183000). The period of record for peak- Although the timing of high-flow events re- flow measurements is longer, extending to 1909 mained constant, the magnitude of these events for Niagara (14181500) and to 1906 for Mehama decreased. The dam operation and its effect on (14183000), than the period of record for collec- streamflow can be seen at Niagara (14181500) tion of continuous discharge at these stations. For (fig. 10), particularly in March and April and both gages, the 1.5-, 10-, 50-, 100-, and 500-year again in August and September. The effect of peak flows decreased in the post-dam period dam operation on streamflow becomes dampened (1953–2010) (table 8). The range of decrease in at the two downstream gages (figs. 11–12). peak flows was greater for the Niagara (14181500) gage (-43 – -81 percent) than the Mehama (14183000) gage (-38 – -44 percent).

Figure 10. Graph showing daily mean streamflow in Reach 1 at North Santiam River at Niagara, Oregon (14181500), water year 1975.

Figure 11. Graph showing daily mean streamflow in Reach 2 at North Santiam River at Mehama, Oregon (14183000), water year 1975.

Figure 12. Graph showing daily mean streamflow in Reach 3 at North Santiam River at Green’s Bridge near Jefferson, Oregon (14184100), water year 1975.

Table 8. Pre- and post-dam flood statistics for selected Santiam River basin, Oregon, streamflow gaging stations, computed from annual peak streamflow data based on the Bulletin 17B Log Pearson III method. [Abbreviations: POR, period of record in water years; ft3/s, cubic feet per second.]

Pre-dam period Post-dam period Recurrence Station Streamflow gaging-station interval Streamflow Streamflow Percent number name and study reach number (years) POR (ft3/s) POR (ft3/s) change 14181500 North Santiam River at Niaga- 1.5 1909– 16,700 1953– 9,540 -43 ra, Oregon, Reach 1 1952 2010 10 44,700 15,200 -66 50 69,600 18,000 -74 100 81,300 19,000 -77 500 111,000 21,100 -81 14183000 North Santiam River at Me- 1.5 1906– 28,500 1953– 17,800 -38 hama, Oregon, Reach 2 1952 2010 10 58,300 32,700 -44 50 79,800 45,500 -43 100 89,000 51,500 -42 500 111,000 67,200 -39 14187500 South Santiam River at Wa- 1.5 1906– 31,500 1967– 14,200 -55 terloo, Oregon, Reach 6 1966 2010 10 65,600 20,900 -68 50 91,300 24,800 -73 100 103,000 26,300 -74 500 130,000 29,700 -77 14189000 Santiam River at Jefferson, 1.5 1908– 62,400 1953– 44,200 -29 Oregon, Reach 7 1952 2010 10 152,000 102,000 -33 50 231,000 157,000 -32 100 268,000 184,000 -31 500 364,000 259,000 -29

Under regulated streamflow conditions, the Niagara (14181500) and Mehama (14183000), median of annual 1-day maximum streamflows at respectively, median monthly streamflows in- the three North Santiam River gages at Niagara creased in July and August as a result of dam (14181500), Mehama (14183000), and Green’s regulation. However, for Reach 3, median month- Bridge (14184100) decreased by 42 to 50 percent ly streamflows decreased in July and August, be- for 1953–2009 compared to computed unregulat- cause the regulated streamflow time series, based ed streamflow conditions (table 9). In contrast, on measured data, includes surface-water with- the median of annual 7-day minimum stream- drawals for municipal water use and irrigation in flows increased by 25 to 93 percent at these three Reach 3. The unregulated time series, computed stations (table 10). The median monthly stream- by the USACE, does not take into account these flows at all three gages decreased in the late win- withdrawals because it was created for the pur- ter and spring (February–June) and all increased pose of quantifying the effects of the dams on in the late summer to winter (September– streamflow. January) (table 11). For the Reach 1 and 2 gages, Table 9. One-day maximum annual streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon. [Regulated and unregulated streamflows based on observed and computed data as described in the text. Medians computed from the 1-day maximum annual flows for the period of record.] Unregulated Regulated Period of streamflow streamflow Reach Station record (wa- median median Percent number number Streamflow gaging station name ter years) (ft3/s) (ft3/s) change 1 14181500 North Santiam River at Niagara, 1953–2009 17,900 10,300 -42 Oregon

2 14183000 North Santiam River at Mehama, 1953–2009 28,700 14,500 -49 Oregon

3 14184100 North Santiam River at Greens 1953–2009 32,200 16,000 -50 Bridge near Jefferson, Oregon

4 14186500 Middle Santiam River at mouth 1967–2009 16,400 9,950 -39 near Foster, Oregon

5 14186700 South Santiam River at Foster, 1967–2009 24,900 11,900 -52 Oregon

6 14187500 South Santiam River at Waterloo, 1967–2009 27,700 13,600 -51 Oregon

7 14189000 Santiam River at Jefferson, Ore- 1953–2009 71,800 43,900 -39 gon

Table 10. Seven-day minimum annual streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon. [Regulated and unregulated streamflows based on observed and computed data as described in the text. Medians were computed from the 7-day minimum annual flows for the period of records.]

Unregulated Regulated Period of streamflow streamflow Reach Station record median median Percent number number Streamflow gaging station name (water years) (ft3/s) (ft3/s) change 1 14181500 North Santiam River at Niagara, 1953–2009 579 928 60 Oregon 2 14183000 North Santiam River at Mehama, 1953–2009 554 1,070 93 Oregon 3 14184100 North Santiam River at Greens 1953–2009 620 773 25 Bridge near Jefferson, Oregon 4 14186500 Middle Santiam River at mouth 1967–2009 85.6 52.6 -39 near Foster, Oregon 5 14186700 South Santiam River at Foster, 1967–2009 155 636 310 Oregon 6 14187500 South Santiam River at Waterloo, 1967–2009 145 631 335 Oregon 7 14189000 Santiam River at Jefferson, Oregon 1953–2009 359 1,210 237

Table 11. Median monthly streamflow statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon. [POR, Period of record; WY, water year from October 1 to September 30. ft3/s, cubic feet per second. Regulated and unregulated streamflows based on observed and computed data as described in the text. Medians computed from monthly flows for the period of records.]

Reach Station POR in Streamflow January February March April May June July August September October November December number number WY condition (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) (ft3/s) 1 14181500 1953– Unregulated 2,610 2,400 2,420 2,710 2,660 1,700 937 687 665 760 1,720 2,470 2009 Regulated 2,900 1,090 1,050 1,420 2,220 1,530 1,090 1,020 1,780 2,360 3,060 3,020 Percent change 11 -55 -57 -48 -17 -10 16 48 168 211 78 22 2 14183000 1953– Unregulated 4,180 3,680 3,740 3,980 3,610 2,160 1,090 755 721 891 2,670 3,930 2009 Regulated 5,050 2,690 2,530 2,780 3,270 2,070 1,270 1,120 1,880 2,490 4,140 5,350 Percent change 21 -27 -32 -30 -9 -4 17 48 161 179 55 36 3 14184100 1953– Unregulated 4,680 4,120 4,190 4,450 4,040 2,420 1,220 845 807 998 2,990 4,400 2009 Regulated 5,460 2,820 2,630 2,850 3,250 1,880 983 830 1,710 2,480 4,400 5,780

Percent change 17 -32 -37 -36 -20 -22 -19 -2 112 148 47 31 29

4 14186500 1967– Unregulated 2,340 1,880 1,960 1,880 1,410 641 228 126 147 273 1,560 2,350 2009 Regulated 2,660 526 568 993 1,290 673 599 631 1,060 1,340 2,310 3,570 Percent change 14 -72 -71 -47 -9 5 163 401 621 391 48 52 5 14186700 1967– Unregulated 3,660 2,970 3,020 3,010 2,250 1,030 377 210 228 426 2,340 3,680 2009 Regulated 4,390 1,680 1,700 2,220 1,770 1,040 743 708 1,110 1,560 3,300 5,350 Percent change 20 -43 -44 -26 -21 1 97 237 387 266 41 45 6 14187500 1967– Unregulated 4,220 3,570 3,710 3,540 2,500 1,120 388 206 251 489 2,650 4,270 2009 Regulated 5,180 2,390 2,360 2,760 2,050 1,120 771 691 1,150 1,660 3,570 6,000 Percent change 23 -33 -36 -22 -18 0 99 235 358 239 35 41 7 14189000 1953– Unregulated 10,800 9,370 9,270 9,020 6,940 3,470 1,160 551 639 1,280 6,060 10,300 2009 Regulated 12,700 7,960 7,330 7,270 6,280 3,520 1,690 1,370 2,480 3,920 8,550 13,000 Percent change 18 -15 -21 -19 -10 1 46 149 288 206 41 26

For the Reach 1 gage, North Santiam River 15). For low-flow periods, the 95-percent stream- at Niagara (14181500), the 5-percent streamflow flow exceedance increased for all three of the exceedance under regulation decreased by about North Santiam River gages by 13 to 75 percent. 6 percent (table 12). Changes in the 5-percent This is typical for low flows with reservoir regu- streamflow exceedance as a consequence of regulation. It is also noteworthy that the increase in lation at the Reach 2 and 3 gages, Mehama low flows is less noticeable at the Reach 3 gage (14183000) and Green’s Bridge (14184100), because of major water withdrawals between the were less than 2 percent (table 12 and figs. 13– Reach 2 and 3 gages (fig. 15). Table 12. Streamflow exceedance statistics from regulated and unregulated daily mean streamflows for the Santiam River, Oregon. [POR, Period of record; WY, water year from Oct. 1 to Sept. 30. cfs, cubic feet per second. Regulated and unregulated streamflows based on observed and computed data as described in the text.] Percent of daily mean streamflow, in cubic feet per second, equaled or Reach Station Streamflow exceeded number number POR in WY condition 5 10 25 50 75 90 95 1 14181500 1953–2009 Unregulated 5,910 4,380 2,810 1,680 864 635 583 Regulated 5,560 4,640 2,880 1,680 1,050 958 900 Percent change -5.9 5.8 2.4 0.2 21 51 54 2 14183000 1953 –2009 Unregulated 9,660 6,870 4,270 2,420 1,040 685 593 Regulated 9,680 6,970 4,130 2,450 1,590 1,150 1,040 Percent change 0.2 1.4 -3.3 1.3 53 68 75 3 14184100 1953 –2009 Unregulated 10,800 7,680 4,780 2,710 1,170 767 663 Regulated 10,600 7,520 4,420 2,430 1,440 882 752 Percent change -1.8 -2.1 -7.5 -10 23 15 13 4 14186500 1967 –2009 Unregulated 5,770 3,890 2,190 1,050 263 126 97 Regulated 4,940 4,310 2,130 1,040 557 294 53 Percent change -14 11 -2.7 -1.0 112 133 -46 5 14186700 1967 –2009 Unregulated 8,730 5,950 3,410 1,640 421 208 167 Regulated 8,930 6,130 3,230 1,530 830 686 612 Percent change 2.3 3.0 -5.3 -6.7 97 230 266 6 14187500 1967 –2009 Unregulated 9,880 6,880 4,000 1,950 470 222 164 Regulated 10,300 7,050 3,810 1,840 957 709 629 Percent change 4.2 2.5 -4.7 -5.6 104 220 283 7 14189000 1953 –2009 Unregulated 24,600 17,000 10,100 5,120 1,280 551 386 Regulated 25,100 17,500 9,750 5,120 2,570 1,480 1,200 Percent change 2.0 3.1 -3.2 0.1 100 169 211

Figure 13. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 1 at North San- tiam River at Niagara, Oregon (14181500), water years 1953–2009.

Figure 14. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 2 at North San- tiam River at Mehama, Oregon (14183000), water years 1953–2009.

Figure 15. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 3 at North San- tiam River at Green’s Bridge near Jefferson, Oregon (14184100), water years 1953–2009.

South Santiam River discharges were exceeded on average only 0.18 and 0.02 times per year, respectively. The one The longest streamflow time series in the time the flood threshold was exceeded in the South Santiam River basin was recorded at South post-dam period was February 7, 1996, at 24,200 Santiam River at Waterloo (14187500), which ft3/s. If the dams had not been constructed, the has been in continuous operation since 1923 (fig. USACE estimated that this event would have 16). The highest daily mean streamflow in the been 83,800 ft3/s at Waterloo (14187500). record was on December 22, 1964, at 77,000 ft3/s prior to the construction of the Green Peter and Using annual peak flows, which have been Foster Dams in 1967. Prior to dam regulation, measured at the Waterloo (14187500) gage since daily mean streamflow exceeded the USACE de- 1906, flood frequencies were separately comput- fined bankfull and flood threshold discharges on ed for the pre-dam (1906–1966) and post-dam average 4.12 and 1.72 times per year, respective- (1967–2010) periods. As a result of dam regula- ly, for the period from the start of water year tion, the 1.5-, 10-, 50-, 100-, and 500-year peak 1924 to the end of water year 1966. For water flows decreased by 55 to 77 percent (table 8). years 1967–2011, bankfull and flood threshold

Figure 16. Graph showing daily mean streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1924–2011.

Following a similar pattern as the North San- gage (Reach 4) shows the effects of regulation tiam gages, a comparison of measured and com- from Green Peter Dam. The Reach 5 gage is on puted unregulated mean daily streamflows (water the South Santiam River at Foster (14186700) years 1967–2009) at the three South Santiam just below Foster Dam. Farther downstream, in River basin gages (Reaches 4–6) showed that Reach 6, the streamflow record for Waterloo February–May streamflows decreased and July– (14187500) at RM 23.3 shows the effects of Fos- November streamflows increased under regulated ter Dam streamflow regulation combined with streamflow conditions (figs. 17–19). The Middle unregulated inflow from Wiley, Ames, and Santiam River at mouth near Foster (14186500) McDowell Creeks.

Figure 17. Graph showing mean daily streamflow in Reach 4 at Middle Santiam River at mouth near Foster, Ore- gon (14186500), water years 1967–2009.

Figure 18. Graph showing mean daily streamflow in Reach 5 at South Santiam River at Foster, Oregon (14186700), water years 1967–2009.

Figure 19. Graph showing mean daily streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1967–2009. A comparison of measured regulated and the measured streamflow at the Reach 5 gage computed unregulated daily mean streamflows at (14186700) (fig. 21), which is below Foster Dam. these three gages (Reaches 4–6) during a single Because one of the objectives of Foster Dam is average hydrologic year (1975) showed the ef- re-regulating Green Peter Dam discharge, meas- fects of dam regulation in the annual hydrograph ured streamflow below Foster Dam appears more (figs. 20–22). Green Peter Dam operation and its natural and less regulated than streamflow from effect on streamflow at the Reach 4 gage Green Peter Dam. (14186500) (fig. 20) is evident in comparison to

Figure 20. Graph showing daily mean streamflow in Reach 4 at Middle Santiam River at mouth near Foster, Ore- gon (14186500), water year 1975.

Figure 21. Graph showing daily mean streamflow in Reach 5 at South Santiam River at Foster, Oregon (14186700), water year 1975.

Figure 22. Graph showing daily mean streamflow in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water year 1975. Under regulated streamflow conditions for was compiled from reservoir modeling output 1967–2009, the median annual 1-day maximum and contained many consecutive days of exactly streamflow at the three gages (Middle Santiam 50 ft3/s of discharge. River at mouth near Foster [14186500], South The median monthly streamflows at the three Santiam River at Foster [14186700], and South Reach 4–6 gages (Middle Santiam River at mouth Santiam River at Waterloo [14187500]) de- near Foster [14186500], South Santiam River at creased by 39 to 52 percent in comparison to Foster [14186700], and South Santiam River at computed unregulated streamflow conditions (ta- Waterloo [14187500]) decreased in the late win- ble 9). In contrast, the median of annual 7-day ter and spring (February–May) and increased minimum streamflows increased by 310 to 335 from summer to winter (July–January) as a result percent at Foster (14186700) and Waterloo of dam regulation (table 11). (14187500) gages, respectively (table 10). Both those gages are downstream from Foster Dam. For the two gages below Foster Dam, South However, for the gage below Green Peter Dam Santiam at Foster (14186700) and at Waterloo (Middle Santiam River at mouth near Foster (14187500), the 5-percent streamflow exceedance [14186500]), the median annual 7-day minimum increased slightly (less than 5 percent) under reg- streamflow decreased by 39 percent. Summer low ulation (figs. 23–25; table 12). The 95-percent flows commonly increased as a result of dam streamflow exceedance increased 266 and 283 regulation. The decrease in low flows for the percent for gages 14186700 and 14187500, re- Reach 4 gage below Green Peter Dam may have spectively. However, the 95-percent streamflow been because of an error in the regulated stream- exceedance for the gage below Green Peter Dam flow time series. The 1967–2009 regulated (14186500) decreased by 46 percent, possibly streamflow time series for this station was entire- because of an error in the computed streamflow ly computed because the gage was discontinued time series as previously mentioned. in 1966. The time series, provided by USACE,

Figure 23. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 4 at Middle Santiam River at mouth near Foster, Oregon (14186500), water years 1967–2009.

Figure 24. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 5 at South Santiam River at Foster, Oregon (14186700), water years 1967–2009.

Figure 25. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 6 at South Santiam River at Waterloo, Oregon (14187500), water years 1967–2009.

Main-Stem Santiam River the North and South Santiam River basins because those gages are closer to the dams. In addi- The Santiam River at Jefferson (14189000) tion to the greater travel time, the effect of the gage began continuous operation in water year dams is also decreased at the Jefferson 1940 and is downstream from all four USACE (14189000) gage because of substantial natural dams (Detroit, Big Cliff, Green Peter, and Foster) inflow between the dams and the station. (fig. 26). Although the effect of the four dams is evident in this streamflow record, the effect is less than the effect seen in the streamflow data in

Figure 26. Graph showing daily mean streamflow in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water years 1940–2011.

Prior to construction of the North Santiam was a wet period. The effect of flood control in River dams in 1953, daily mean streamflow ex- the North and South Santiam Rivers likely is ceeded the USACE defined bankfull and flood comparable because the drainage area above Fos- threshold discharges on average 7.46 and 1.92 ter Dam (492 mi2) is comparable to the drainage times per year, respectively. During water years area above Big Cliff Dam (449 mi2). Also, at 1953–2011, daily mean streamflow exceeded their confluence, the drainage areas of the North bankfull and flood threshold discharges on aver- and South Santiam Rivers are 1,770 and 1,810 age 4.12 and 0.66 times per year, respectively. mi2, respectively. The largest flood events in the post-dam regula- Using annual peak flows, which have been tion period were 143,000 ft3/s (December 23, 3 measured at the Jefferson (14189000) gage start- 1964) and 115,000 ft /s (February 7, 1996). If the ing in 1908, flood frequencies were separately dams had not been constructed, the USACE esti- computed for the pre-dam (1908–1952) and post- mated that these two events would have been dam (1953–2010) periods. As a result of dam 219,000 ft3/s (December 22, 1964) and 240,000 3 regulation, the 1.5-, 10-, 50-, 100-, and 500-year ft /s (February 7, 1996) (fig. 26). The full effect peak flows decreased by 29 to 33 percent (table of flood control does not appear until water year 8). This is substantially less than the peak-flow 1967 when the South Santiam dams were com- decreases computed for the gages in the North pleted. Although it may appear that the North and South Santiam River basins because those Santiam River dams provide less flood control gages are upstream closer to the dams. than the South Santiam River dams, it should be noted that the late 1950s and early 1960s (before Similar to the North and South Santiam Riv- construction of the South Santiam River dams) er gages, a comparison of measured and computed unregulated mean daily streamflows (water

years 1953–2009) at the Jefferson (14189000) (fig. 27). Because the Jefferson (14189000) gage gage showed that February–May streamflows de- is farther downstream from the dams, the effect creased and July–November streamflows in- of streamflow regulation caused by the dams is creased under regulated streamflow conditions less pronounced than at the upstream gages.

Figure 27. Graph showing mean daily streamflow in Reach 7 at Santiam River at Jefferson , Oregon (14189000), water years 1953–2009.

A comparison of measured regulated and dam operation that is noticeable in the hydro- computed unregulated daily mean streamflows at graphs for North Santiam River at Niagara the Jefferson (14189000) gage during a single (14181500) and Middle Santiam River near Fos- average hydrologic year (1975) showed the ef- ter (14186500), which are both immediately fects of dam regulation (fig. 28). Flood peaks downstream from Big Cliff and Green Peter were reduced in magnitude and streamflows were Dams, respectively, does not appear in the Jeffer- higher in September and October. The day-to-day son (14189000) hydrograph.

Figure 28. Graph showing daily mean streamflow in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water year 1975.

Under regulated streamflow conditions from flows at the Jefferson (14189000) gage decreased 1953 to 2009, the median of annual 1-day maxi- in the late winter and spring (February–May) and mum streamflows at the Jefferson (14189000) increased in the summer to early winter (June– gage decreased by 39 percent (table 9). However, January) as a result of dam regulation (table 11). the median of annual 7-day minimum stream- The 5-percent streamflow exceedance increased flows increased by 237 percent (table 10). The slightly (less than 5 percent), whereas the 95- median monthly streamflows were consistent percent streamflow exceedance increased by 211 with the median monthly streamflows at the six percent (fig. 29, table 12). upstream gages (Reaches 1–6). Monthly stream-

Figure 29. Graph showing percent of daily mean streamflows equaled or exceeded in Reach 7 at Santiam River at Jefferson, Oregon (14189000), water years 1953–2009.

Geomorphic and Ecological Synopsis this study used information from Gregory and others (2007a, 2007b) that provided a broad This section provides a brief assessment of summary of species and habitats for the geomorphic and ecological characteristics within Willamette River basin. Other datasets used in the Santiam River basin and their responses to this Santiam assessment include U.S. Department streamflow. The findings from this assessment of Agriculture National Agriculture Imagery Pro- are based primarily on qualitative observations gram (NAIP) 2009 digital orthophotographs (1-m and simple measurements drawn from existing resolution); a Quaternary geology map datasets and a review of prior relevant studies. (O’Connor and others, 2001); locations of Because a comprehensive spatially explicit study USACE revetments (Jerry Otto, U.S. Army Corps of terrestrial and aquatic habitats and species of of Engineers, written commun., Jan 13, 2012); concern is lacking for the Santiam River basin, and a land-cover map from 1850 (Gregory and

others, 2002a). General summary reports includ- reach is under constant inundation by the down- ing the Willamette Project Biological Opinions stream Foster Lake reservoir. (National Marine Fisheries Service, 2008; U.S. Fish and Wildlife Service, 2008), Biological As- North Santiam River Channel Morphology sessment (U.S. Army Corps of Engineers, 2007), The upper 2.8 mi of Reach 1 is bounded by and watershed assessments (E and S Environ- Detroit and Big Cliff Dams. Downstream from mental Chemistry Inc., 2002; E and S Environ- the dams, the North Santiam River transitions mental Chemistry Inc. and South Santiam Water- from a narrow channel confined by steep bedrock shed Council, 2000) also were used. Previous valley walls to a broad, alluvial river with numer- studies of historical channel change in the San- ous side channels and gravel bars before joining tiam River basin (Fletcher and Davidson, 1988; the South Santiam River near Jefferson. Between Klingeman, 1973), as well as other nearby basins, Big Cliff Dam (RM 58.1) and the USGS gage at including the Willamette (Wallick and others, Niagara (14181500) (RM 57.3), the North San- 2006, 2007), Middle and Coast Fork (Gregory tiam River flows predominantly over bedrock and and others, 2002a, 2002b) and McKenzie River coarse bed material through a narrow canyon basins (Risley and others, 2010a, 2010b) also with few gravel bars. Downstream from the bed- were incorporated in this study. rock rapids near the town of Niagara (RM 55.0), Geomorphic Characteristics of Study Reaches the flood plain widens to about 0.6 mi, and active gravel bars begin to appear, though they are small In the following section, geomorphic charac- (2,000–3,000 yds2) and typically more than a teristics of the North, South, and main-stem San- mile apart (fig. 30). There are several large (up to tiam Rivers are briefly summarized and dis- 16,000 yd2) densely vegetated mid-channel bars played. More complete descriptions for each near the downstream end of Reach 1 near the Lit- reach are provided in Appendix D. Although the tle North Santiam River confluence. Channel and Middle Santiam River (Reach 4) is listed in Ap- flood-plain confinement owing primarily to basin pendix C, it is not described in this section be- topography throughout Reach 1 limit channel cause it has limited habitat potential owing to re- complexity and flood-plain processes; however, leases from the upstream Green Peter Dam that small, relict secondary channel features such as likely scour the channel in the upper portion of those between RM 40 and RM 44 may provide the reach and because the lower portion of the off-channel habitat at high flows.

Figure 30. Aerial photograph showing channel and flood-plain morphology in study Reach 1 of the Santiam River basin, Oregon, on the North Santiam River.

Downstream from the Little North Santiam North Santiam River below RM 35 flows through River, the flood plain of the North Santiam River a broad flood plain and historically probably dis- along Reach 2 widens from 0.2 mi to nearly 1.5 played an anastomosing planform, meaning the mi as the channel adopts an increasingly com- river had multiple converging and diverging plex, multi-threaded morphology (fig. 31). Just channels separated by large, semi-stable islands below the upstream boundary of Reach 2, the riv- much like the upper Willamette River above Har- er flows through a short, confined segment where risburg as described in Gregory and others the flood plain is about 0.2 mi wide and is closely (2002b). Presently, many of the secondary chan- flanked by Pleistocene terraces (fig. 31). Within nel features along Reach 2 are densely vegetated, this segment, historical channel change has likely and flow is mainly confined to a single channel, been minimal, and a specific gage analysis by except for RM 26–33, where the active channel is Klingeman (1973) found little indication of ag- over 0.25 mi wide and accommodates a diverse gradation or incision between 1935 and 1965 at array of side channels, alcoves, islands, and grav- the USGS streamflow gage at Mehama el bars (fig. 31). (14183000) (RM 38.7). Farther downstream, the

Figure 31. Surficial geology and revetments for alluvial segments of the Santiam River, Oregon, study area. Late Pleistocene alluvium is a combination of units Qff2, Qg1, and Qg2; Holocene alluvium is a combination of units Qalc, Qalf, Qau, and Qbf; all other units shown from O’Connor and others (2001).

Channel complexity increases downstream found throughout the entire reach. An example of along North Santiam River through Reach 3. This a segment in Reach 3 containing modern channel historically dynamic, multi-channeled reach is complexity and relict channel features is shown flanked by a broad flood plain 0.7–1.5 mi wide in figure 32. Because there is little revetment (fig. 31). Active gravel bars up to 25,000 yd2 in along the North Santiam River in Reaches 2 and area are present throughout the reach and are 3 (fig. 31), channel processes including meander nearly continuous along the multi-channeled migration, bar growth and creation, and mainte- segment near RM 17–21 (fig. 32). While nearly nance of secondary channel features are mainly half of Reach 3 presently displays complex, mul- determined by the flow and coarse-sediment re- ti-channeled planform, densely vegetated, relict gimes. These processes have been altered by up- secondary channel and flood-plain features are stream dams.

Figure 32. Aerial photograph showing channel and flood-plain morphology in study Reach 3 of the Santiam River basin, Oregon, on the North Santiam River.

South Santiam River Channel Morphology analysis at the USGS gage at Waterloo (14187500) (RM 23.3) near the boundary be- Historically, the lower South Santiam River tween Reach 5 and Reach 6 indicates minimal between RM 0 and RM 18 along Reach 6 likely change in bed elevation between 1935 and 1965 displayed a complex, anastomosing planform. (Klingeman, 1973) underscoring the overall sta- Presently, this segment, as well as Reach 5 (14.7 bility of this segment of the South Santiam River. mi of channel below Foster Dam), primarily oc- There is only one area with moderate channel cupies a low-sinuosity, single-thread channel (fig. complexity along Reach 5 (between RM 28 and 31). Although the flood plain in Reach 5 varies RM 29) where the river is flanked on both sides from 0.1 mi wide near Sweet Home to nearly 1 by Holocene alluvium and has multiple channels. mi wide elsewhere, much of the channel flows Active gravel bars are sparse throughout Reach 5 against naturally occurring hard surfaces includ- and are relatively small (less than 1,500 yd2). The ing the flood-plain margin and basalt underlying reach has a number of densely vegetated bar sur- the valley walls that limits channel complexity faces such as the island at RM 36 (fig. 33). and provides stability (fig. 3). A specific gage

Figure 33. Aerial photograph showing channel and flood-plain morphology in study Reach 5 of the Santiam River basin, Oregon, on the South Santiam River.

The South Santiam River along Reach 6 can Foster and Big Cliff Dams resulted in substantial be divided into two distinct segments. From RM reductions in channel complexity and gravel-bar 18 (Lebanon) to its confluence with the North area. For example, Fletcher and Davidson (1988) Santiam River, the river flows through a broad reported a 56-percent reduction in the area of Holocene flood plain 1.75–3 mi wide that histori- gravel bars between 1936 and 1981. The 2009 cally had a dynamic, multi-thread channel. Up- orthophotographs show numerous bare, active stream between RM 18 and RM 23, the river gravel bars up to 25,000 yd2, downstream from flowed through a relatively narrow flood plain RM 18 in areas lacking bank revetment (for ex- (0.2–0.8 mi wide) that historically supported a ample, RM 4.5 in fig. 34). Gravel bars and chan- more stable, single-thread channel (fig. 31). Alt- nel complexity is much less where one or both hough the channel in the lower segment (RM 0– banks are stabilized with revetment (Fletcher and 18) is flanked on both sides by easily erodible Davidson, 1988; as depicted between RM 5 and Holocene alluvium and was historically prone to RM 6 in fig. 34). Downstream from RM 18, ex- rapid meander migration, much of the reach is tensive formerly active bar surfaces and relic sec- presently stabilized by revetments constructed in ondary channel features are presently stabilized the mid-to-late 20th century (fig. 31). Bank stabi- with dense vegetation (for example, RM 5–7 in lization in combination with construction of the fig. 34).

Figure 34. Aerial photograph showing channel and flood-plain morphology in study Reach 6 of the Santiam River basin, Oregon, on the South Santiam River.

Main-Stem Santiam River Channel Morphology bank erosion, channel complexity, and bar growth (fig. 31). Between the confluence of the The main-stem Santiam River below the con- South and North Santiam Rivers and RM 10, the fluence of the North and South Santiam Rivers channel is confined by sedimentary rocks (fig. historically formed dynamic multi-thread chan- 31). Large, bare, active gravel bars are intermit- nels that were prone to rapid meander migration tent but can exceed 100,000 yd2, especially in the and avulsion prior to flood control and bank pro- lower 5 mi of Reach 7 near its confluence with tection. Presently, the Santiam River along Reach the Willamette River (fig. 35). Throughout the 7 is mainly confined to a single channel (fig. 31) reach, there are many relict bar surfaces and sec- with several sections where flow is split by mid- ondary channel features that presently have dense channel bars (for example, RM 5.3 in fig. 35). vegetative cover. However, these features may be Although Reach 7 flows through a broad flood activated during exceptionally high flows (fig. plain that ranges up to 3 mi wide, revetment cur- 35). rently flanks much of the channel, restricting

Figure 35. Aerial photograph showing channel and flood-plain morphology in study Reach 7 of the Santiam River basin, Oregon, Santiam River main stem. Specific gage analyses at the USGS gage at ecological responses to geomorphic and hydro- Jefferson (14189000) (RM 9.6) for the period logic processes can include (1) fish spawning in 1941–1986 shows substantial (greater than 1 ft) gravel substrates created from flooding; (2) fish erosion from 1941 to 1964 (Klingeman, 1973) migration and spawning in response to minimum and then relatively stable channel conditions from streamflows and cooler stream temperatures; or 1964 to 1986 (Fletcher and Davidson, 1988). (3) cottonwood seed dispersal in response to fresh Fletcher and Davidson (1988) attribute these bare ground exposure caused by flood scouring. overall changes to initial scouring of alluvial de- The Santiam River basin historically provided posits and later cross-section control by an ex- diverse habitats that supported many aquatic and posed bedrock outcrop slightly downstream. This terrestrial ecosystems. Many of these habitats bedrock outcrop is probably a remnant from the have been substantially altered by modifications adjacent Pleistocene terraces composed of partial- in the river’s flow and sediment transport or are ly cemented gravels (unit Qg1) (fig. 31), which inaccessible because of passage issues at dams can form resistant shoals and riffles (Wallick and and culverts. Gregory and others (2007a, 2007b) others, 2006). Therefore, the specific gage analy- and Risley and others (2010a) provide detailed sis for the Jefferson gage may not be representa- synopses of aquatic and terrestrial species likely tive of other locations in this reach because the to be affected by flow modifications in the Mid- bank materials here are not the easily erodible dle and Coast Fork Willamette and McKenzie Holocene alluvium found elsewhere along this River drainages. A brief summary of key ecolog- reach. ical species and habitat needs are outlined below and are provided by reach in Appendix D. Terrestrial and Aquatic Habitats and Key Spe- cies The multi-channel segments with off-channel and secondary features along the North Santiam Geomorphic processes in response to stream- River below RM 33 and the main-stem Santiam flow are critical for creating and maintaining River below RM 7 provide off-channel and aquatic and terrestrial habitat. A few examples of backwater habitats critical for species such as Or-

egon chub, red legged frog, and western pond sediment regimes and previous environmental turtle (Gregory and others, 2007a, 2007b). These flow studies in the Willamette River basin. segments also have secondary channel features With a wide active channel, abundance of and sloughs that provide high-flow refugia and gravel bars and secondary channel features, and rearing habitat for native fish, including spring limited revetments, the lower North Santiam Riv- Chinook and winter steelhead. Although these er below RM 33 would likely respond dynamical- features are present on the South Santiam River ly to environmental flow releases. Channel and below RM 18, they are much less extensive be- flood-plain response to high-flow releases (in- cause of revetments and channel simplification cluding high-flow pulses and small and large than on the North Santiam River. Other native floods) may include meander migration and pos- fish species that use the North, South, and main- sibly avulsions at very high discharges. Bank ero- stem Santiam Rivers include rainbow trout, cut- sion from meander migration and avulsions throat trout, northern pike minnow, sand rollers, would likely supply coarse bed-material sediment shiners, sculpins, and dace (Gregory and others, for deposition downstream, forming gravel bars, 2007a, 2007b). riffles, pools, and spawning habitats. Bank ero- The broad, low-gradient flood plains of the sion along forested portions of the flood plain Santiam River historically contained a complex could introduce large wood into the active chan- mosaic of riparian forests and wetlands, which nel, providing cover and habitat complexity for has been simplified throughout the study area fish, amphibians, and mammals and possible since the 1850s. Presently, the riparian forest cor- blockages that support further bar growth and ridor is nearly contiguous along lower North San- pool formation. High flows may also support the tiam River below RM 33, the South Santiam Riv- maintenance and creation of secondary channel er below RM 18, and the main-stem Santiam features; scour stabilizing vegetation from relict River below RM 7. Within these sections, the gravel bars depending on flow magnitude; and forest corridor ranges in width from a narrow assist with seed dispersal, organic matter ex- band of trees to more than 0.7 mi (as shown in change between the river and riparian areas, and figs. 32, 34, and 35) and likely includes tree spe- deposition of sediment suitable for seedling ger- cies such as black cottonwood, riparian willows, minations. and white alder (Gregory and others, 2007a, Reaches lined by revetment or naturally oc- 2007b). These species are associated with the curring material resistive to erosion may have more dynamic multi-channel stretches because more limited responses to flow modifications. For they depend on high flows in winter and spring instance, Reach 6 of the South Santiam below for seed dispersal, active sediment transport and RM 18 has extensive revetment that limits bank deposition to create exposed fine sediment patch- erosion, recruitment of gravel and large wood es for germination, and erosion to remove canopy from the flood plain, and creation of new habitats cover that otherwise may preclude establishment. suitable to riparian vegetation establishment. Be- Potential Geomorphic and Ecological Re- cause revetments have also restricted lateral mi- sponse to Environmental Flow Releases gration and limited bar growth along the South Santiam River (Fletcher and Davidson, 1988), No comprehensive study relating streamflow environmental flow releases on the South San- with specific geomorphic or ecological responses tiam may not be as effective at increasing bar ar- exists for the Santiam River basin. Hence, the ea and spawning habitat as they might be on the following section discusses possible effects of lower North Santiam River, which has fewer re- environmental flow releases on physical habitat vetments. Other areas unlikely to display dynam- and riparian ecosystems based on known rela- ic channel response to environmental flow releas- tions between channel processes and flow and es include the stable semi-consolidated gravel

and bedrock dominated segments of the study flow and, probably, stream-temperature fluctua- area including the North Santiam River (Reaches tions because spawning of spring Chinook salm- 1 and 2) above RM 33 and the South Santiam on is especially heavy in this area (National Ma- River above RM 18 (Reaches 4, 5, and 6). rine Fisheries Service, 2008, section 4.5). Rela- Another important consideration of environ- tions between life history and monthly stream- mental flow releases is the possibility of channel flow and stream temperature similar to those de- incision and bed coarsening in response to high veloped for the Middle and Coast Fork flows caused by sediment trapping behind the Willamette and McKenzie Rivers (Gregory and dams. The dams on the North and South Santiam others, 2007a, 2007b; Risley and others, 2010a) Rivers trap sediment from 59 and 47 percent of could assist in developing basin-specific envi- these basins, respectively. The beds of down- ronmental flow releases for the Santiam River stream reaches have likely coarsened in response basin. to excess transport capacity because dams limit Streamflow patterns also influence other sediment supply (National Marine Fisheries Ser- aquatic and riparian species. For example, ex- vice, 2008; Fletcher and Davidson, 1988). There- treme low-flow periods, which can be exacerbat- fore, it is possible that high-flow releases may ed by withdrawals, can lower groundwater levels further coarsen the bed or trigger bed-level lower- and threaten the survival of riparian seedlings ing, especially along alluvial segments where such as black cottonwood and white alder (Greg- there are limited upstream sources of bed material ory and others, 2007a, 2007b). In contrast, large from tributaries or bank erosion. Further assess- floods may erode young trees on low-lying flood- ment of the influence of environmental flow re- plain surfaces, but they can also disperse seeds leases on bed coarsening and channel lowering and stems and deposit fresh sediment patches at would entail development of a bed-material lower elevations within the active channel, where budget along with a comprehensive analysis of new seedlings can germinate, ultimately increas- historical changes in grain size and bed eleva- ing the diversity and age classes of riparian vege- tions. tation (Gregory and others, 2007a, 2007b). To In addition to modifying physical habitat, assist in the development of environmental flow streamflow also affects the spawning, rearing, releases that aim to increase the diversity and age and migration behavior of fish species. Discharge classes of native riparian forests, relations be- during autumn increased throughout the study tween streamflow and riparian vegetation could area, which coincides with late summer and early be created for the Santiam River basin similar to autumn spawning by spring Chinook and is fol- those developed for the Middle and Coast Fork lowed by lower than historical flows during the Willamette and McKenzie River basins (Gregory late winter (table 11). Such flood-control opera- and others, 2007a, 2007b; Risley and others, tions in late winter may lead to dewatering of 2010a). salmon redds and could potentially kill incubat- ing eggs and alevins (Reiser and White, 1983). Future Studies Additionally, stream-temperature regimes have This study provides a framework and base- been modified by flow regulations, causing tem- line information for developing environmental peratures to be cooler in summer and warmer in flow guidelines in the Santiam River basin. Cen- autumn (Rounds, 2010). Changes to the thermal tral to a sound environmental flow program is regime can have a direct impact on salmonid establishing robust, quantitative relations between outmigrations in winter and spawning and incu- streamflow, channel and flood-plain processes, bation in fall (Gregory and others, 2007a, 2007b). and ecosystem response. These relations can be Reach 5 of the South Santiam River between RM quantified by (1) understanding existing channel 30 and RM 35 may be especially sensitive to such

and flood-plain processes (post-dam, post- Bed-Material Transport Rates and Sediment revetment) along lower, alluvial reaches, (2) un- Budget derstanding relations between environmental flows and terrestrial and aquatic habitats and spe- A sediment budget for the Santiam River ba- cies, and (3) documenting existing conditions and sin would help assess the effects of environmen- those following environmental flow releases of tal flow releases on channel erosion and aggrada- different magnitudes. Such information would tion, which affect the quality of terrestrial and provide a solid basis for evaluating future hydro- aquatic habitats. The budget would focus on es- logic, geomorphic, and ecological changes and timates and (or) measurements of bed-load comprehensive adaptive management in the San- transport, which carries gravel and other material tiam River basin. To address the three objectives that build and maintain spawning habitats, gravel above, it will be necessary to evaluate streamflow bars, and other low-elevation features within the data and analyses, bed-load material transport active channel. By comparing the volumes of rates and sediment budget, channel and flood- gravel exiting the Santiam River basin to the vol- plain morphology, and terrestrial and aquatic re- ume of gravel delivered to the study area and the sponses to environmental flows. volume released through bank erosion, future channel change under different flow and sedi- Streamflow Data and Analysis ment-release scenarios can be evaluated. Modeling and predicting channel and habitat Because sediment budgets rely on sediment response to environmental flow releases requires transport rates, which are difficult to measure, an streamflow information, particularly for peak approach for developing a sediment budget might flows, when bed-material transport, bank erosion, include several of the following methods to esti- and off-channel habitat creation occurs. Although mate sediment transport: there is currently a good network of gages 1. Sediment flux estimates based on bed- throughout the Santiam River basin, additional load transport equations (Wallick and oth- streamflow and stage monitoring (both continu- ers, 2010, 2011). Bed-load transport equa- ous and partial-record) are needed in high- tions calculate transport capacity, and be- priority, multi-thread reaches to relate geo- cause bed-material supply has been sub- morphic processes (such as flood-plain inunda- stantially reduced by the Santiam River tion and scouring of secondary channels) with basin dams, most downstream reaches are streamflow. Streamflow data can be tied with likely supply limited (meaning the ecological information, such as hydrologic con- transport capacity of the river exceeds the nectivity between main-stem and off-channel available supply of sediment). Sediment habitats during high flows and flow recession, to flux estimates from bed-load transport better assess the specific impacts of environmen- equations applied to alluvial reaches will tal flow releases on habitat availability to target likely provide an estimate of maximum species. plausible transport. In addition to new data collection, one- or 2. Direct measurements of bed-load two-dimensional hydraulic modeling can be used transport to verify bed-load transport to estimate water-surface elevations during low- equations and to estimate bed-load fluxes. flow conditions in reaches that are affected by Ideally, such measurements would be col- surface-water withdrawals and possible dam op- lected near active USGS gages and down- erations. This type of modeling can predict habi- stream from potentially gravel-rich tribu- tat loss caused by the dewatering of side channels taries to provide accurate estimates of to- and alcoves in alluvial flood plains. tal bed-material flux into the lower, alluvial reaches.

3. Empirical GIS-based sediment-yield anal- 2007a, 2007b) and the McKenzie River basin yses, factoring in sediment production, (Risley and others, 2010a) are available for use in delivery to the channels, in-channel attri- neighboring basins. Additionally, developing tion, and trapping by dams (Wallick and flow-management strategies to benefit terrestrial others, 2011). and aquatic species and habitats would be further 4. Sediment flux estimates based on mapped supported by (1) documentation of terrestrial and changes in bank erosion and bar area over aquatic conditions representing post-dam stream- specific temporal intervals (Wallick and flow and sediment-transport conditions and the others, 2010). Volumetric change in bank baseline for determining the success of future erosion and bar area can be calculated by flow restorations and (2) supplemental assess- comparing high-resolution topographic ments before and after environmental flow re- data such as LiDAR from two time peri- leases of different magnitudes to assess terrestrial ods in alluvial reaches. This component and aquatic responses and to adapt flow releases can also serve as a basis for monitoring to meet restoration targets. long-term changes in channel and flood- plain conditions. Detailed Channel and Flood-Plain Morphology Assessment A detailed assessment of channel morphology in the Santiam River study area is needed to better understand current channel and habitat conditions and predict changes under different environmental flow scenarios. Mapping channel and flood-plain conditions for different time periods using high-resolution aerial photographs could serve as the starting point for more comprehensive temporal analyses of morphological trends. For example, detailed analyses of changes in channel features (for example, bar area and secondary channel features) could be related to patterns of erosion, deposition, and establishment of vegetation. These analyses will require ac- counting for the uncertainties associated with the mapping protocols and differences in discharge between the aerial photographs. Terrestrial and Aquatic Responses To predict ecological response to flow management, knowledge of the relations between streamflow, water temperature, sediment fluxes, and species of concern and available habitats specific to the Santiam River basin is essential. However, at present, only generalized relations developed for the Middle and Coast Fork Willamette River basins (Gregory and others,

The Detroit and the Big Cliff Dams, on the North Summary Santiam River, were put into service in 1953. In This report provides a baseline assessment of 1968 the Green Peter and Foster Dams were the hydrology, geomorphology, and effect of completed in the South Santiam River basin. The streamflow on the ecology of the Santiam River, dams are operated to provide flood control, hy- a tributary of the Willamette River in northwest- dropower production, irrigation, water supply, ern Oregon. The assessment was made for the recreation, water-quality improvement, and Santiam River environmental flow study, which aquatic habitat. Surface-water withdrawals within is a collaborative effort of the U.S. Army Corps the Santiam River basin for municipal water sup- of Engineers, The Nature Conservancy, and the ply and irrigation are made at various locations U.S. Geological Survey (USGS) under auspices downstream from the dams. The Lebanon- 3 of the Sustainable Rivers Project. In 2002, The Santiam Canal diverts approximately 90 ft /s Nature Conservancy and the U.S. Army Corps of from the South Santiam River upstream from Engineers began the Sustainable Rivers Project Lebanon. The USGS has operated a network of for the purpose of modifying dam operations and continuous streamflow monitoring throughout the implementing environmental flow requirements Santiam River basin since the 1920s. The stations for various river systems around the country. In- with the longest streamflow records are the North formation from this report can assist water man- Santiam River at Mehama (14183000: 1921– agers and stakeholders in the development of fu- 2011) and the South Santiam River at Waterloo ture environmental flow requirements for the (14187500: 1923–2011). Santiam River basin. Seven river reaches, each having distinct The Santiam River basin has an area of 1,810 streamflow, geomorphic, and ecological condi- mi2; elevations range from 162 ft at the tions, were defined for the study area. The North Willamette River confluence to almost 10,500 ft Santiam River was divided into three reaches be- in the Cascade Range. The two main tributaries in tween Detroit Dam and the confluence with the the basin are the North and South Santiam Rivers, South Santiam River. The South Santiam River which join approximately 9 mi upstream from the was also divided into three reaches between Willamette River. Higher elevations in the basin Green Peter Dam and the North Santiam River are underlain by young, relatively permeable ma- confluence. The final reach along the main-stem terial consisting of High Cascade volcanic rocks Santiam River is between the confluence of the and glacial deposits. Middle and lower elevations North and South Santiam Rivers and the of the basin contain older, weathered, less perme- Willamette River confluence. able volcanic material characteristic of the West- To assess the effects of dams and withdraw- ern Cascades. The lower reach in the wide uncon- als on the streamflow regime, measured daily strained flood plain near the Willamette conflu- mean streamflow and annual peak-flow data were ence is composed of Quaternary alluvium. Down- compiled and used to compute statistics that de- stream reaches of the basin are mostly privately scribe regulated and unregulated conditions. In all owned and used for agriculture. Approximately seven study reaches, the dams had the effect of 70 percent of the basin is forested. The basin has decreasing annual high flows. For the North San- long, cool, wet winters and warm, dry summers. tiam River Reaches 1, 2, and 3, the median of an- Average daily maximum and minimum tempera- nual 1-day maximum streamflows decreased 42, tures at Stayton from 1951 to 2011 were 63 and 50, and 50 percent, respectively, under regulated 42°F, respectively. streamflow conditions. Likewise in the South The U.S. Army Corps of Engineers owns and Santiam River basin, the median of annual 1-day operates four dams in the Santiam River basin. maximum streamflows for Reaches 4, 5, and 6 decreased 39, 52, and 51 percent, respectively. In

contrast to their effect on high flows, the dams river with many side channels and gravel bars had the effect of increasing low flows. The medi- before joining the South Santiam River near Jef- an of annual 7-day minimum flows in six of the ferson. Overall, there is little revetment along the seven study reaches increased under regulated North Santiam study reaches. streamflow conditions from 25 to 334 percent The South Santiam River below Foster Dam depending on the reach. On a seasonal basis, me- occupies mostly a low-sinuosity, single-thread dian monthly streamflows decreased from Febru- channel with a flood plain. Active gravel bars are ary to May and increased from September to Jan- sparse and small (less than 1,500 yd2). Instead, uary in all the reaches. However, the magnitude the reach has a number of densely vegetated bar of these changes usually decreased in the reaches surfaces relict of gravel bars that were active be- farther downstream from dams because of natural fore dam and revetment construction. Much of tributary and groundwater inflow entering the the reach presently is stabilized by revetments river below the dams. At the North Santiam River constructed in the mid- to late 20th century. Bank at Mehama gage, bankfull discharge was exceed- stabilization, in combination with construction of ed on average 3.39 times per year prior to con- the Foster and Big Cliff Dams, resulted in sub- struction of the dams in 1953. After the dams stantial reductions in channel complexity. were built, bankfull discharge has been exceeded on average only 0.97 times per year. Farther The main-stem Santiam River below the con- downstream from the dams at the Santiam River fluence of the North and South Santiam Rivers at Jefferson gage, bankfull discharge was exceed- historically had dynamic, multi-thread channels ed on average 7.46 times per year prior to the that were prone to rapid meander migration and construction of the dams in 1953. After the dams avulsion prior to flood control and bank protec- were built, bankfull discharge has been exceeded, tion. The reach flows through a broad flood plain on average, 4.12 times per year. Climatic differ- that ranges up to 3 mi wide. However, bank re- ences between the pre- and post-dam periods also vetment currently flanks much of the channel, were assessed in the study. A Wilcox rank-sum restricting bank erosion, channel complexity, and test of monthly precipitation data from Salem and bar growth. Many relict bar surfaces and second- Waterloo found no significant difference between ary channel features presently have dense vegeta- the two periods. That would suggest that the op- tive cover. eration of the dams since the 1950s and 1960s is Historically, the Santiam River basin sup- the primary cause of alterations to the Santiam ported diverse aquatic and terrestrial ecosystems River basin streamflow regime. ranging from steep, pool-riffle channel systems, The geomorphology and the possible geo- abundant large wood, and riparian forests domi- morphic and ecological changes in response to nated by upland species in the upper reaches to river-flow modifications were characterized. The dynamic multi-thread channels containing off- characterization was based primarily on qualita- channel and secondary features, with alder and tive observations and information from previous cottonwood forests flanking and interacting with studies. Channel processes, including meander the channel in the lower reaches and main stem. migration, bar growth, and creation and mainte- Similar to the Middle and Coast Fork Willamette nance of secondary channel features, are mainly and McKenzie River basins, many of these habi- determined by the flow and coarse-sediment re- tats have been substantially altered by modifica- gimes; however, these processes have been al- tions in the river flow and sediment regimes or tered by flow releases from the upstream dams. are inaccessible because of passage issues at dams. The streamflow analysis and geomorphic The North Santiam River below Big Cliff characterization provide a framework to develop Dam transitions from a narrow channel confined by steep bedrock valley walls to a broad, alluvial

environmental flows to restore the historic di- Lee, K.K., and Hinkle, S.R., 2005, Ground- verse aquatic and terrestrial ecosystems. water hydrology of the Willamette basin, Ore- Suggestions for future ecological monitoring gon: U.S. Geological Survey Scientific Investi- and investigations in the Santiam River basin in- gations Report 2005–5168, 83 p. clude additional streamflow data collection and Cooper, R., 2002, Determining surface water analysis, computing bed-material transport rates availability in Oregon: State of Oregon Water and a sediment budget, a detailed channel and Resources Department Open-File Report SW flood-plain morphology assessment, and deter- 02–002, 157 p. mining terrestrial and aquatic responses to E and S Environmental Chemistry, Inc., 2002, streamflow management. North Santiam River watershed assessment: Corvallis, Oregon, 290 p. (Available online at: Acknowledgements http://www.nsantiamwatershed.org/wp- con- The authors thank Christine Budai, Keith tent/uploads/2009/09/NSW_Assessment.pdf). Duffy, Jerry Otto, and Greg Taylor, Portland Dis- trict, U.S. Army Corps of Engineers; Leslie Bach, E and S Environmental Chemistry, Inc., and The Nature Conservancy, Portland, Oregon; Mike South Santiam Watershed Council, 2000, South McCord and Michael Mattick, Oregon Water Re- Santiam watershed assessment: Corvallis, Ore- sources Department; and Jay Spillum, U.S. Geo- gon, 224 p. (Available online at: logical Survey Oregon Water Science Center for http://www.sswc.org/wp- their assistance in this study. content/uploads/2008/12/South-Santiam- Watershed-Assessment-January-2000.pdf). References Cited Fletcher, W.B., and Davidson, L.D., 1988, South Santiam River Bank Protection Study, Pilot Acreman, M., and Dunbar, M.J., 2004, Defining Project for Willamette River Bank Protection environmental flow requirements–A review: Study: Portland, Oregon, U.S. Army Corps of Hydrology and Earth System Sciences, v. 8, no. Engineers, 36 p. 5, p. 861–876. Gregory, S., Ashkenas, L., Haggerty, P., Oetter, Bragg, H.M., Sobieszczyk, Steven, Uhrich, M.A., D., Wildman, K., Hulse, D., Branscomb, A. and and Piatt, D.R., 2007, Suspended-sediment Van Sickle, J., 2002a, Riparian vegetation, in loads and yields in the North Santiam River ba- Hulse, D., Gregory, S., and Baker, J., eds., sin, Oregon, water years 1999-2004: U.S. Geo- Willamette River basin atlas: Corvallis, Ore- logical Survey Scientific Investigations Report gon, Oregon State University Press, p. 40. 2007–5187, 27 p. (Available online at Bragg, H.M., and Uhrich, M.A., 2010, Suspend- http://www.fsl.orst.edu/pnwerc/wrb/Atlas_web_ ed-sediment budget for the North Santiam Riv- com- er basin, Oregon, water years 2005–08: U.S. pressed/4.Biotic_Systems/4c.riparian_veg_web. Geological Survey Scientific Investigations pdf.) Report 2010–5038, 26 p. Gregory, S., Ashkenas, L., Oetter, D., Minear, P. Buccola, N.L., and Rounds, S.A., 2011, Simulat- and Wildman, K., 2002b, Historical ing potential structural and operational changes Willamette River channel change, in Hulse, D., for Detroit Dam on the North Santiam River, Gregory, S., and Baker, J., eds., Willamette Oregon—Interim Results: U.S. Geological River basin atlas: Corvallis, Oregon, Oregon Survey Open-File Report 2011–1268, 25 p. State University Press, p. 18–24. (Available Conlon, T.D., Wozniak, K.C., Woodcock, Doug- online at http://www.fsl.orst.edu/pnwerc/wrb/ las, Herrera, N.B., Fisher, B.J., Morgan, D.S.,

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http://www.deq.state.or.us/wq/tmdls/docs/willa River drainages, Cascade Range, Oregon: Ore- mettebasin/willamette/ordermemo.pdf . gon Geology, v. 58, no. 5, 103 p. Oregon Water Resources Department, 2012, Wa- Sobieszczyk, Steven, Uhrich, M.A., and Bragg, ter use reporting database: accessed March 7, H.M., 2007, Major turbidity events in the North 2012, at Santiam River basin, Oregon, water years http://apps.wrd.state.or.us/apps/wr/wateruse_r 1999–2004: U.S. Geological Survey Scientific eport/. Investigations Report 2007-5178, 51 p. Piatt, D.R., Johnston, M.W., Bragg, H.M., Speers, D.D., and Versteeg, J.D., 1982, Runoff Brooks, A.M., Sobieszczyk, Steven, and forecasting for reservoir operations—The past Uhrich, M.A., 2011, Water-quality in the North and the future (Santiam River basin, Detroit Santiam River basin, Oregon—Comparison of reservoir), Proceedings of the Eastern Snow water-quality data for water year 2007 with the Conference, 39th annual meeting, April 19–23, preceding period of record: U.S. Geological Reno, Nevada: p. 149–156. Survey Open-File Report 2011–1008, 75 p. Sullivan, A.B., and Rounds, S.A., 2004, Model- Reiser, D.W., and White, R.G., 1983, Effects of ing streamflow and water temperature in the complete redd dewatering on salmonid egg- North Santiam and Santiam Rivers, Oregon, hatching success and development of juveniles: 2001–02: U.S. Geological Survey Scientific In- Transactions of American Fisheries Society, v. vestigations Report 2004–5001, 36 p. 112, p. 532-540. Sullivan, A.B., Rounds, S.A., Sobieszczyk, Ste- Richter, B.D., Warner, A.T., Meyer, J.L., and ven, and Bragg, H.M., 2007, Modeling hydro- Lutz, K., 2006, A collaborative and adaptive dynamics, water temperature, and suspended process for developing environmental flow rec- sediment in Detroit Lake, Oregon: U.S. Geo- ommendations: River Research and Applica- logical Survey Scientific Investigations Report tions, v. 22, p. 297–318, DOI: 10.1002/rra.892. 2007–5008, 40 p. Risley, John, Wallick, J.R., Waite, Ian, and Tharme, R.E., 2003, A global perspective on en- Stonewall, Adam, 2010a, Development of an vironmental flow assessment: emerging trends environmental flow framework for the McKen- in the development and application of envi- zie River basin, Oregon: U.S. Geological Sur- ronmental flow methodologies for rivers: River vey Scientific Investigations Report 2010– Research and Applications, v. 19, p. 397–441, 5016, 94 p. DOI: 10.1002/rra.736. Risley, J.C., Bach, L., and Wallick, J.R., 2010b, Thayer, T.P., 1936, Geology of the Salem Hills Summary report—Environmental flows work- and the North Santiam River basin, Oregon: shop for the McKenzie River, Oregon: The Na- Oregon Department of Geology and Mineral ture Conservancy, Portland, Oregon, 40 p. Industries, Bulletin no. 15, 40 p. Rounds, S.A., 2010, Thermal effects of dams in Thayer, T.P., 1936, Structure of the North San- the Willamette River basin, Oregon: U.S. Geo- tiam River section of the Cascade Mountains in logical Survey Scientific Investigations Report Oregon: The Journal of Geology, v. 44, no. 6, 2010–5153, 64 p. p. 701-716. Sherrod, D., Ingebritsen, S.E., Curless, J.M., The Nature Conservancy, 2007, Indicators of hy- Keith, T.E., Diaz, N.M., and DeRoo, T.G., and drologic alteration—Version 7 User’s manual: Hurlocker, S.L., 1996, Water, rocks, and The Nature Conservancy, 75 p., accessed De- woods; a field excursion to examine the geolo- cember 19, 2011, at gy, hydrology, and geothermal resources in the http://conserveonline.org/workspaces/iha/docu Clackamas, North Santiam, and McKenzie ments/download/view.html.

The Nature Conservancy, 2009, The Sustainable http://water.usgs.gov/osw/streamstats/index.ht Rivers Project: accessed November 18, 2011, at ml. http://www.nature.org/ourinitiatives/habitats/ri Wallick, J.R., Lancaster, S.T., and Bolte, J.P., verslakes/sustainable-rivers-project.xml 2006, Determination of bank erodibility for Uhrich, M.A., and Bragg, H.M., 2003, Monitor- natural and anthropogenic bank materials using ing instream turbidity to estimate continuous a model of lateral migration and observed ero- suspended-sediment loads and yields and clay- sion along the Willamette River, Oregon— water volumes in the Upper North Santiam USA: River Research and Applications, v. 22, River basin, Oregon, 1998–2000: U.S. Geolog- p. 631–649. ical Survey Water Resources Investigation Re- Wallick, J.R., Grant, G.E., Lancaster, S.T., Bolte, port 03–4098, 44 p. J.P., and Denlinger, R.P., 2007, Patterns and U.S. Army Corps of Engineers (USACE), 2007, controls on historical channel change in the Supplemental biological assessment of the ef- Willamette River, Oregon, in Gupta, A.V., ed., fects of the Willamette River basin flood con- Large rivers—Geomorphology and manage- trol project on species listed under the Endan- ment: John Wiley and Sons, p. 491–516. gered Species Act—Submitted to National Ma- Wallick, J.R., Anderson, S.W., Cannon, Charles, rine Fisheries Service and U.S. Fish and Wild- and O’Connor, J.E., 2010, Channel change and life Service, [variously paged]: accessed May bed-material transport in the lower Chetco Riv- 22, 2012, at er, Oregon: U.S. Geological Survey Scientific http://www.nwp.usace.army.mil/Portals/24/doc Investigations Report 2010–5065, 68 p. s/environment/biop/Final_Will_Suppl_BA.pdf Wallick, J.R., O'Connor, J.E., Anderson, Scott, U.S. Fish and Wildlife Service (USFWS), 2008, Keith, Mackenzie, Cannon, Charles, and Ris- Final Biological Opinion on the continued op- ley, J.C., 2011, Channel change and bed- eration and maintenance of the Willamette Riv- material transport in the Umpqua River basin, er basin Project and effects to Oregon Chub, Oregon: U.S. Geological Survey Scientific In- Bull Trout, and Bull Trout Critical Habitat des- vestigations Report 2011–5041, 112 p., ac- ignated under the Endangered Species Act— cessed November 10, 2011, at Submitted to U.S. Army Corps of Engineers, http://pubs.usgs.gov/sir/2011/5041/. Bonneville Power Administration, and Bureau Western Regional Climate Center, 2012, Web- of Reclamation, [variously paged]: accessed site—Cooperative climatological data summar- January 16, 2012, at ies: accessed June 14, 2012, at http://www.nwr.noaa.gov/Salmon- http://www.wrcc.dri.edu/climatedata/climsum/. Hydropower/Willamette-basin/Willamette- BO.cfm. Wolman, M.G., and Miller, J.P., 1960, Magnitude and frequency of forces in geomorphic pro- U.S. Geological Survey, 2012, StreamStats: ac- cesses: Journal of Geology, v. 68, no. 1, p. 54– cessed March 7, 2012, at 74.

Appendix A. Streamflow Data Time-Series Extension Microsoft Excel files containing the daily mean streamflow data time-series extensions for each of the study reaches can be downloaded by clicking on the links below. http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach1.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach2.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach3.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach4.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach5.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach6.xls http://pubs.usgs.gov/of/2012/1133/Flow_extension.reach7.xls In each file, there is a “Read me” worksheet that explains how the streamflow time series for the reach was extended to cover missing periods. Each file also includes computed unregulated daily-mean streamflow data time series, provided by the U.S. Army Corps of Engineers, which were used in the study. The equations used to compute the unregulated daily-mean streamflow time series are provided in Appendix B. Appendix B. U.S. Army Corps of Engineers Computed Unregulated Streamflow Data Time Series This appendix contains methods and equations from U.S. Army Corps of Engineers used to compute six daily mean unregulated streamflow time series for the Santiam River basin (Keith Duffy, U.S. Army Corps of Engineers, written commun., 2011). One or more of these six time series were used in each of the seven Excel files described in Appendix A. However, all six time series are shown together in the worksheet labeled “2. Unregulated flow” in the Reach7.xls Excel file.

1. North Santiam River at Detroit Dam 10/01/1935–09/30/1938 Combined observed flows of: USGS 14178000 (North Santiam River above Boulder Creek near Detroit, Oregon) and USGS 14179000 (Breitenbush River above French Creek near Detroit, Oregon) Plus local inflows computed as: USGS 14183000 (North Santiam River at Mehama, Oregon) Minus the sum of: USGS 14182500 (Little North Santiam River near Mehama, Oregon), USGS 14178000 (lagged by 6 hours), and USGS 14179000 (lagged by 6 hours) Adjusted by a drainage area ratio (DAR) of 0.509

10/01/1938–10/30/1952 Observed flow of: USGS 14181500 (North Santiam River at Niagara, Oregon) Adjusted by DAR (0.960)

10/01/1952–09/30/1960 Calculated inflow (Modified Flows) Adjusted by DAR (0.960)

10/01/1960–09/30/2009 Quality controlled Dataquery project inflows

2. Local inflows to North Santiam River at Mehama, Oregon (14183000) 10/01/1935–09/30/1938 Observed flow of: USGS 14172500 (Little North Santiam River near Mehama, Oregon) Plus local inflows computed as: USGS 14183000 (North Santiam River at Mehama, Oregon) Minus the sum of: USGS 14182500 (Little North Santiam River near Mehama, Oregon), USGS 14178000 (lagged by 6 hours), and USGS 14179000 (lagged by 6 hours) Adjusted by DAR (0.491)

10/01/1938–09/30/2009 Observed flow of: USGS 14183000 (North Santiam River at Mehama, Oregon) Minus routed flow of: USGS 14181500 (North Santiam River at Niagara, Oregon) Adjusted by DAR (1.091)

3. Middle Santiam River at Green Peter Dam 10/01/1935–09/30/1947 Observed flow of: USGS 14186000 (Middle Santiam River near Foster, Oregon)

10/01/1947–09/30/1950 Observed flow of: USGS 14185000 (South Santiam River below Cascadia, Oregon) Adjusted by regression coefficient (2.022)

10/01/1950–09/30/1966 Observed flow of: USGS 14186500 (Middle Santiam River at mouth near Foster, Oregon) Adjusted by DAR (0.959)

10/01/1966–06/21/1967 Combined observed flow of: USGS 14185800 (Middle Santiam River near Cascadia, Oregon) and USGS 14185900 (Quartzville Creek near Cascadia, Oregon) Sum adjusted by regression coefficient (1.245)

06/22/1967–09/30/2009 Calculated inflow (Dataquery)

4. Local inflows to South Santiam River at Foster Dam 10/1/1935–8/22/1968 Observed flow of: USGS 14185000 (South Santiam River below Cascadia, Oregon) Adjusted by regression coefficient (1.194)

8/23/1968–9/30/2009 Calculated inflow (Dataquery) minus Green Peter outflow (Dataquery)

5. Local inflows to South Santiam River at Waterloo, Oregon (14187500) 10/01/1935–09/30/1947 Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus combined routed flow of: USGS 14185000 (South Santiam River below Cascadia, Oregon) and USGS 14186000 (Middle Santiam River near Foster, Oregon) Adjusted by DAR (0.761)

10/01/1947–09/30/1950 Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus routed flow of: USGS 14185000 (South Santiam River below Cascadia, Oregon) Adjusted by DAR (0.318)

10/01/1950–09/30/1966 Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus combined routed flow of: USGS 14185000 (South Santiam River below Cascadia, Oregon) and USGS 14186500 (Middle Santiam River at mouth near Foster, Oregon) Adjusted by DAR (0.829)

10/01/1966–07/31/1973 Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus routed flow of: USGS 14186700 (South Santiam River at Foster, Oregon)

08/01/1973–09/29/1988

Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus routed flow of: USGS 14187200 (South Santiam River near Foster, Oregon) Adjusted by DAR (1.037) Plus routed flow of: USGS 14187100 (Wiley Creek at Foster, Oregon)

09/30/1988 -09/30/2009 Observed flow of: USGS 14187500 (South Santiam River at Waterloo, Oregon) Minus routed flow of: USGS 14187200 (South Santiam River near Foster, Oregon) Adjusted by DAR (1.164) Plus routed flow of: USGS 14187000 (Wiley Creek near Foster, Oregon)

6. Local inflows to Santiam River at Jefferson, Oregon (14189000) 10/01/1935–09/30/1939 Observed flow of: USGS 14191000 (Willamette River at Salem, Oregon) Minus combined routed flows of: USGS 14187500 (South Santiam River at Waterloo, Oregon), USGS 14183000 (North Santiam River at Mehama, Oregon), and USGS 14174000 (Willamette River at Albany, Oregon) Adjusted by DAR (0.433)

10/01/1939–09/30/2009 Observed flow of: USGS 14189000 (Santiam River at Jefferson, Oregon) Minus combined routed flows of: USGS 14187500 (South Santiam River at Waterloo, Oregon)

USGS 14183000 (North Santiam River at Mehama, Oregon)

Appendix C. Indicators of Hydrologic Alteration Results Microsoft Excel files containing the results of the Indicator of Hydrologic Alteration analysis for each of the study reaches can be downloaded by clicking on the links below. http://pubs.usgs.gov/of/2012/1133/IHA.reach1.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach2.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach3.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach4.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach5.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach6.xls http://pubs.usgs.gov/of/2012/1133/IHA.reach7.xls

Appendix D. Description of Study Reaches A Microsoft Excel spreadsheet containing descriptions of the seven study reaches may be accessed at http://pubs.usgs.gov/of/2012/1133/appendix_d.

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